THE FISH CREEK CANYON ICHNOFAUNA: A PLIOCENE (BLANCAN) VERTEBRATE FOOTPRINT ASSEMBLAGE FROM ANZA-BORREGO DESERT STATE PARK, CALIFORNIA

PAUL REMEIKA

Anza-Borrego Desert State Park, 200 Palm Canyon Drive, Borrego Springs, CA, 92004

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Abstract— An ubiquitous avian and mammaloid hoof- and footprint vertebrate ichnofauna is identified from basin-margin sediments in the Vallecito-Fish Creek Basin of Anza-Borrego Desert State Park, California. The terrestrial assemblage is one of the most varied yet discovered from late Pliocene (Blancan) deposits. Seven morphofamilies are recognized, represented by nine ichnospecies with morphologic parameters quantified. Four new ichnospecies are herein proposed. The ichnofauna includes Gruipeda diabloensis, a small ansiodactyl bird; Mustelidichnum vallecitoensis (new), an aquatic musteloid; Chelipus therates, a typical carnivorian canoid; Pumaeichnum milleri, an intermediate feloid; P. stouti (new), a large feloid; Hippipeda downsi, a monodactyl equoid; Lamaichnum borregoensis, a small llamoid; Megalamaichnum albus (new), a large llamoid; and Stegomastodonichnum garbanii (new), a probable gomphotherioid. Most mammaloid trackmakers are hitherto unknown from the fossil record of the study area but do occur within the known osteological record of the stratigraphically younger Vallecito Badlands.

Footprints are preserved as positive ceiling casts on the undersides of thick, overhanging sandstone ledges, or as natural negative floor impressions associated with various interstratified, dessication mud drapes. Well-documented tracksites occur throughout multiple stratigraphic levels of a vertical-continuous mixed-affinity marine-deltaic (Yuha Formation), delta-plain (Palm Spring Formation), and fluvial-alluvial fan (Ocotillo Formation) transition zone exposed between Hanging Tracks Wash in the Fish Creek Badlands (Blancan II), and Arroyo Tapiado in the Vallecito Badlands (Blancan IV-V). The majority of tracksites occur below and above Fish Creek Canyon (Blancan III). This report provides a significant treatise on identification for, and expansion of, the morphological ranges known among Neogene vertebrate ichnotracks of western North America.

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INTRODUCTION

The Neogene basin-margin sedimentary fill of the structurally-depressed Vallecito-Fish Creek Basin half-graben was deposited under terrestrial conditions in response to the kinematics of lithospheric extension (Remeika, 1995, 1997). Such high energy environments typically are poorly fossiliferous in terms of a vertebrate body-fossil record. Although microvertebrate material of the Arroyo Seco Local Fauna (Downs and White, 1968; Cunningham, 1984; White et al., 1991) and a significant silicified wood paleoflora (Remeika et al., 1988; Remeika, 1994) is documented from these deposits, the most spectacular fossil resource is its vertebrate ichnofauna, yielding a surprisingly good census of bird, musteloid, canoid, feloid, equoid, llamoid, and gompotherioid. Given the restricted nature of other fossils, the stratigraphic abundance of tracks warrants greater attention as a significant component of paleontologic research, contributing to our understanding of the temporal, spatial distribution, and paleoecology of the Fish Creek Canyon Ichnofauna (Remeika, 1999) during the Pliocene Epoch.

Altogether, nine vertebrate ichnospecies are documented herein from three recognized lithofacies that share a complex mixed-affinity depositional architecture: basinal fine-grained marine-deltaic clays and silts of the Yuha Formation (Remeika, 1998a) sourced from the Gulf of California, delta-plain arenites of the progradational Palm Spring Formation (Woodring, 1931) sourced from the Colorado Plateau, and locally-derived syn-extensional fluviatile facies distributions of medial alluvial fan sandstones mapped regionally as the Ocotillo Formation (Remeika, 1992, 1997), sourced from the Canebrake Conglomerate (Dibblee, 1954). Isolated footprints, sets of tracks, and lesser trackways are relatively common, concentrated on beach clays or multiple flood-plain depositional paleosurfaces (subaerially-exposed mudflats) as either positive ceiling molds or negative floor casts. Their abundance confirms an importance as a consistent rather than occasional resource in the fossil record and proves that, under certain conditions, a discrete depositional package (basin-margin) can be a favorable repository of preferentially preserved vertebrate tracks.

ABBREVIATIONS

The following abbreviations are acronyms for institutions and repositories of ichnites cited herein: IVCM _vertebrate paleontology collections previously housed in the Imperial Valley College Museum, El Centro, California; ABDSP _vertebrate paleontology collections of the California Department of Parks and Recreation, Colorado Desert District, Anza-Borrego Desert State Park, Borrego Springs, California; SRC _Stout Research Center and paleontology laboratory, Anza-Borrego Desert State Park, Borrego Springs, California. Stratigraphically-controlled Anza-Borrego Zones, utilizing lithologic markers, after Downs and White (1968). North American Land Mammal Age chronology after Repenning (1987). Identifications herein employed and emended follow the tentative binomial synonymy of avian and mammaloid paleoichnologic classifications after Vialov (1965, 1966), Aramayo and Manera de Bianco (1987, 1996), Leonardi (1987), and Sarjeant and Langston (1994) and attempts to preserve the original ichnogenera assignations following recommendations set forth in Article 23.1 of the International Code of Zoological Nomenclature, Fourth Edition. The Greek affix _ichnum (= -ichnium), meaning "trace fossil of a …" is preferred in most instances, and is emended herein in order to preserve the neutrality of the masculine suffix _ichnus. All specimen numbers preceded with a "V" represent ABDSP vertebrate specimens. Specimen numbers followed by an "A" represent plaster cast replicas.

GEOLOGIC SETTING
simplified maps of Anza-Borrego Desert State Park

Figure 1. Simplified map of Anza-Borrego Desert State Park (shaded), with general location of the Vallecito-Fish Creek Basin (dashed box), location of specific badlands areas (solid boxes), and vicinity of tracksites (solid circle).

Setting. _ The Vallecito-Fish Creek Basin is a 373 km2 upper-plate syn-rift half-graben located 43 km south of Borrego Springs, California (Figure 1). Footprint-bearing strata are located along the north-central basin-margin. This area contains an organization of thick asymmetric sedimentary sequences including fault-bounded coarse-grained marginal conglomerates and finer-grained axial/central flood-basin paleofacies distributions that preserve unique ephemeral ichnocoenosis represented by the Fish Creek Canyon Ichnofauna. Altogether, the Miocene-Pleistocene basin-fill geometry represents > 5,000 m of nonmarine, marine, deltaic, and syn-deposited alluvial fan deposition exposed throughout the Carrizo, Fish Creek, and Vallecito Badlands. Sediments are vertically-stacked and shingled, and generally dip west in response to dip-slip activity on the Elsinore Fault Zone east of the presumed breakaway zone of the Western Salton Trough Detachment (Remeika, 1995). Due to its structural intactness, the Vallecito-Fish Creek Basin yields one of the most accessible and best preserved Neogene stratigraphic/paleontologic packages in North America (Remeika and Lindsay, 1992; Remeika et al., 1995; Remeika, 1997). Deposits of the Vallecito Badlands have been subjected to intensive study and fossil collecting since the 1930's by investigators of the American Museum of Natural History, Los Angeles County Museum of Natural History, Imperial Valley College Museum, and Anza-Borrego Desert State Park. This has resulted in well established lithostratigraphy (Downs and White, 1968; White et al., 1991; Remeika, 1995, 1997, 1998a), and magnetostratigraphy (Opdyke et al., 1977; Johnson et al., 1983), especially of the terrestrial deposits between the Fish Creek and Vallecito Badlands. These nonmarine sediments span the Plio-Pleistocene boundary, and are well over 2,000 m thick. Fossil vertebrates are plentiful, and range throughout the alternating marginal/basinal sandstones and finer-grained lacustrine sediments, providing a local record of evolution, immigration, and extinction for the past 2-3 million years.

Study area. _ Vertebrate tracksites occur in multiple stratigraphic levels of a proximal flood-plain paleoenvironment between Hanging Tracks Wash (ABDSP 1727) in the North Fork of Fish Creek Wash and Arroyo Tapiado (ABDSP 1750) in the Vallecito Badlands (Remeika, 1993).

Stratigraphic framework. _ The Yuha Formation consists of terrigenous sediments supplied by theancestral Colorado River into a marginal-marine, tidally-dominated, delta-front environment of the northernmost Gulf of California (Remeika, 1998a). It is distinguished by the infrequent presence of siliciclastic-carbonate, epifaunal oyster-anomiid-dominated coquina beds separated by thick stratigraphic intervals of unfossiliferous, rhythmically-alternating couplets of fine-grained gypsiferous claystone and siltstone. The progradational stacking of rhythmites is laterally-persistent, and a distinctive feature where they occur in upward-coarsening cycles capped by arenites and/or coquina. The Yuha Formation interfingers with nonmarine arenites of the Palm Spring Formation.

The Palm Spring Formation is an extensively-exposed delta-plain deposit debouched by the ancestral Colorado River across the subsiding Salton Trough basin-center. In the Vallecito-Fish Creek Basin, this conspicuous lithofacies is 2,500 m thick (Dibblee, 1954). It represents deltaic progradation and maturation, with increased sediment yield. Sediments include extraregional pale pink to cream-colored, fine to very fine-grained, massive, concretionary, quartzitic arenites and gravelly sandstones with a common vertical pattern of zonation, punctuated stratigraphically by subordinate brown-colored, ripple-laminated, gypsiferous overbank claystones and siltstones. The high percentage of arenites resulted from current-deposited bedload of paleochannel, point bar, or sheetflood deposits that contain cross-bedding structures and textural features are indicative of an outgrowth from a highly meandering fluvial system (Remeika, 1997). The result is relatively persistent, uniform, multilateral arenites that are distinctive in outcrop, oftentimes forming prominent strike ridges. Along the basin-margin, the Palm Spring Formation interfingers with locally-derived sandstones of the Ocotillo Formation.

The Ocotillo Formation is a vertically-stacked, west-southwest thickening sequence of fluvially-deposited medium to coarse-grained alluvial fan sandstones and finer-grained sediments. Exposures in the Fish Creek Badlands represent the medial package of a strongly asymmetric sediment-thickness distribution shed from Canebrake Conglomerate host sequences. Depending upon location, gradation ranges from crudely-bedded, massive granitoid megaboulders to conglomeratic sandstones. Basinward, this unit is restricted by short transport distances along the subsiding axis, and shares an unconfined proximal to distal sandstone-dominated flood-plain relationship with the Palm Spring Formation. Distribution of sediments was controlled by a hydrodynamic regime promoted by high-energy flash flood and related fluvial processes which ultimately transported sands out of channels and across an expansive proximal flood-plain (Remeika, 1997). Gray-colored sandstones and siltstones dominate this sequence, interspersed with several easily distinguished reddish-brown arenitic tongues from the delta-plain. The high-energy sandstone sequences are generally multistory, sheet-like, and unconfined to broadly lenticular geometries with scoured or steeply channelized erosion surfaces. Small-scale planar and broad trough crossbedding, and parallel-laminated sandstones capped by suspension-deposited fines composed of current ripple-laminated claystone/sandstone dominate this setting. Olive-green micaceous silty claystone mud drapes suggest waning flow velocities. Subaerial indicators of exposure on paleosurfaces include desiccation cracks, raindrop impressions, low-energy wave- and adhesion-ripples, run-off channels and rills, and occurrences of a variety of trace fossils including vertebrate footprints.

Age. _ Sedimentary deposits of the Vallecito-Fish Creek Basin cross several magnetic zones of both normal and reversed polarity. A normal remnant magnetic signature is documented in the eastern Vallecito Badlands between Fish Creek Canyon and Arroyo Seco del Diablo (Opdyke et al., 1977; Johnson et al., 1983) (Figure 2). This signature is interpreted to represent the lower normal epoch in the Gauss normal polarity magnetochron. This is bracketed above the Gilbert reversed magnetochron and below two short reversal intervals possibly matching the Mammoth and Kaena magnetosubchrons in the Gauss Normal Chron. An alternate correlation is with the upper normal epoch in the Gauss Normal Chron. This is based on a re-evaluation of the normal epoch at the top of the Vallecito Badlands section interpreted by Opdyke et al. (1977), and Johnson et al. (1983) to be either the Jaramillo or Olduvai normal magnetochrons (Remeika, 1999). It is entirely possible that it represents the Brunhes. Future refinements in the direction of magnetostratigraphy will undoubtedly resolve this problem. Following Johnson et al. (1983), either correlation is consistent with a Pliocene age assignment for the Fish Creek Canyon Ichnofauna (Blancan II-V), and places the age of Fish Creek Canyon at about 3.5 Ma (Blancan III; Cande and Kent, 1995), and Camel Ridge at about 3.3 Ma (Blancan III; Cande and Kent, 1995). The older tracksites ABDSP 1726, 1727, 1740, and 1741 occur in reversely magnetized sediments between the Nunivak and Cochiti normal magnetochrons in the Gilbert Reversed Chron (Joseph C. Liddicoat, written comm., 2001). This correlation places the age of Hanging Tracks Wash at about 4.3-4.5 Ma (Blancan II; Cande and Kent, 1995). The younger tracksites ABDSP 1748, 1749, and 1750 occur above the 2.58 Ma Gauss/Matuyama boundary (Blancan IV-V; Cande and Kent, 1995) in Arroyo Tapiado. This determination is supported by two volcanic ash beds that bracket the tracksites (Anza-Borrego Zone 46); the lowermost ash yields a fission-track date of 2.3 + 0.4 Ma (Johnson et al., 1983). Regionally, the western Vallecito Badlands may be synchronous to the Borrego Badlands of northern Anza-Borrego, constrained to the early Pleistocene (Irvingtonian I-II) based on identified and correlated tephrochronology (chemical fingerprinting of the Bishop and Thermal Canyon ash beds), applied magnetostratigraphy (presence of the Jaramillo normal magnetosubchron and the Brunhes Normal Chron), and presence of age-diagnostic ostracodes (such as Limnocythere bradburyi) and vertebrates (Equus bautistensis, Camelops huerfanensis, and Mammuthus imperator) (Remeika and Jefferson, 1993; Remeika and Beske-Diehl, 1996; Remeika, 1998b).

Composite lithostratigraphy of the basin-margin section between Fish Creek Canyon and Arroyo Seco del Diablo.
Figure 2. Composite lithostratigraphy of the basin-margin section between Fish Creek Canyon and Arroyo Seco del Diablo. The distribution of magnetized polarity epochs is shown to the right of the measured column.

FISH CREEK CANYON ICHNOFAUNA
General view of the Camel Ridge tracksite

Figure 3. General view of the Camel Ridge tracksite (ABDSP [IVCM] 866), featuring well-preserved llamoid natural mold footprint impressions of Lamaichnum borregoensis Remeika, 1999 in hardened claystone. Track horizon 9. Individual impressions measure about 11.8 cm in length, and about 10.5 cm in width

The first vertebrate tracksite discovered in the basin is Camel Ridge ABDSP [IVCM] 866 (Miller et al., 1982a, b) (Figure 3). The majority of footprints are tracks of hoofed didactyl llamoids yielding two distinct populations represented by the ichnospecies Lamaichnum borregoensis, measuring from 12 cm in length, and Megalamaichnum albus measuring from 17 cm in length. These compare favorably with the morphology and size generally attributable to the Pliocene trackmakers Hemiauchenia macrocephala, and H. blancoensis. In addition, small ansiodactyl bird tracks (ichnospecies Gruipeda diabloensis), a feloid footprint (ichnospecies Pumaeichnum stouti), and the musteloid ichnospecies Mustelidichnum vallecitoensis also occur. Three other tracksite discoveries in the Fish Creek Badlands (Stout et al., 1987; Stout and Remeika, 1991) (ABDSP 1727, 1728, and 1729) yield a canoid, and large and small llamoids. These are in close proximity to a densely-trampled megatracksite (ADBSP 1730) dominated by monodactyl equoid tracks of the ichnospecies Hippipeda downsi. ABDSP 1732 is significant, yielding footprint impressions of three ichnotaxa on a single sandstone panel. The isolated natural casts exhibit manus and pes toe and pad digitigrade impressions of a feloid (ichnospecies Pumaeichnum milleri), a canoid with claw marks (ichnospecies Chelipus therates), and an isolated plantigrade footprint of a probable heavy-footed gomphotherioid trackmaker (ichnospecies Stegomastodonichnum garbanii). This footprint has an overall length of 38 cm, an overall breadth of 28 cm, and is impressed into the strata 13.5 cm. At present, twenty-four tracksites are known from the basin, with the largest density impressed between Arroyo Seco del Diablo and the North Fork of Fish Creek Wash.

SYSTEMATIC PALEOICHNOLOGY

DIVISION VERTEBRATICHNIA Vialov, 1966

CLASS AVIPEDIA Vialov, 1966

MORPHOFAMILY GRUIPEDIDAE Sarjeant and Langston, 1994

Ichnogenus Gruipeda Panin and Avram, 1962

Type ichnogenus.- Gruipeda Panin and Avram, 1962:

Diagnosis (emended after Sarjeant and Langston, 1994).- The ichnogenus Gruipeda includes avian footprints that exhibit morphological characters attributable to the Ralliformes, Charadriiformes, and the Ciconiiformes. Gruipeda embraces avian footprints showing four digits, three (II to IV) pointing forward and the fourth (I) pointing or directed posteriorly, its axis may coincide with, or be at an angle to, that of digit III. Digits united or separate proximally. Webbing not present.


Ichnospecies Gruipeda diabloensis Remeika, 1999

V6107, V6263, V6264, V6265, V6266, V6267, V6268

(Figure 4)

photograph of a well-preserved avian Gruipeda diabloensis Remeika

Figure 4. Photograph of a well-preserved avian Gruipeda diabloensis Remeika, 1999 natural mold trackway impression (V6107) in hardened claystone from Camel Ridge. Track horizon 9. Individual footprint impressions measure between 1.3-1.6 cm in digit length.

bird tracks, Miller et al., 1982a: poster session, 1982b: unpaginated.

shorebird tracks of Pluvialis and Charadrius vociferous (Hildegarde Howard, pers. comm., 1984) White et al., 1991: 9.

Avipeda sp. cf. Calidris sp. (sanderling track) Remeika et al., 1995: 90.

Avipeda sp. cf. Tringa sp. (sandpiper track) Remeika et al., 1995: 90.

Avipeda sp. cf. Calidris sp., and Tringa sp. Remeika, 1995: 22; Remeika, 1997: I-18.

fossil avian tracks and trackways Buchheim et al., 1999: 47-52, Figure 2, Figure 3, c-d, Figure 4, a-c, 57.

Gruipeda diabloensis Remeika, 1999: 44, Figure 10, 63.

Holotype.- ABDSP [IVCM] 866/V6107 (Figure 4). Avian trackway faintly impressed on what used to be a moist subaerially-exposed micaceous silty claystone bedding plane surface. Footprints were selected because the impressions are deep enough to leave a clear outline, and retain significant characteristics representative of the majority of footprint impressions. Specimen remains uncollected in situ.

Additional material.- Paratypes, ABDSP 1745/V6263-V6268, and ABDSP 1739/V6269 (unfigured). Specimens accessioned into the fossil vertebrate collections of the SRC. Additional paratypes remain uncollected and unnumbered in situ (Figure 5).
close up photography of a set of avian tracks as a part of a natural mold trackway impression in hardened claystone from Camel Ridge
Figure 5. Close-up photograph of a set of avian (Gruipeda diabloensis) tracks as part of a natural mold trackway impression in hardened claystone from Camel Ridge (unnumbered in situ ). Track horizon 9. Digit III measures approximately 1.6 cm in length for scale. Hammer head also for scale (10 cm).

 

Etymology.- Small avian footprints, named after Arroyo Seco del Diablo, site of discovery.

Diagnosis.- Type specimen represents obligate bipedal footprints made by an ansiodactyl avian trackmaker. Footprints of small size, exhibiting four slender, well-defined pedal digits (toes), one of which (III) is directed forward, II and IV directed outward curving anteriorly at a low angle, and I (hallux) directed backward, and short. The impressions of digits II and IV are similar in length, biconvex, tapering to a pointed tip (claw). Sharp claw on each digit although difficult to identify on the impression. Digit III is longer. Digit I is smaller and slender. The axis of digit I corresponds with, or may be slightly offset from, that of digit III. The average interdigital divarication between digits II and III is 74º and between III and IV is 54º. The impressions of digits I to IV are united proximally. Representative footprints are part of a narrow trackway; stride short. No indication of webbing between the digits.

Dimensions.- Breadth of trackway 3.0 cm; stride length 9.7 cm. Length of digits: I, 0.6-0.7 cm; II, 1.3 cm; III, 1.6 cm; IV, 1.5 cm.

Discussion.- Ansiodactyl avian footprints of Gruipeda diabloensis occur in direct association with the llamoids Lamaichnum borregoensis, Megalamaichnum albus, the musteloid Mustelidichnum vallecitoensis, and the feloid Pumaeichnum stouti at Camel Ridge. The uniformity of preservation indicates that the footprints were ephemeral, impressed within a short period of time. Since there is no indication of mudcracks, the clay was moist enough and not exposed to the drying effects of air for a prolonged period of time prior to burial. The tracks seem to have been made by several individuals of the same species walking in random variable directions.

Locality.- Camel Ridge (Anza-Borrego Zone 35), Arroyo Seco del Diablo, Vallecito-Fish Creek Basin, approximately 34 km east of Canebrake, California. The exact locality ABDSP [IVCM] 866, is on file at the SRC. A second locality, ABDSP 1745, represents the northern extension of Camel Ridge. A third locality, ABDSP 1739 reported by Buchheim et al. (1999: 49, Figures 3, c-d; 50, Figures 4, a-c), occurs in Fish Creek Wash, and is on file at the SRC. The avian footprints (V6269) at this tracksite remain uncollected in situ.

Horizon.- Fluvial thin-bedded micaceous silty claystone interbed of the Ocotillo Formation. Track horizon 9.

Age.- Holotype and paratypes V6263-V6269: late Pliocene (Blancan III).

Possible affinity of the trackmaker.- Fossil footprints of Gruipeda diabloensis were informally compared to modern Calidris alba (sanderling) and Calidris mauri (sandpiper) avian shorebird tracks (Paul Jorgensen, pers. comm., 1994). This was based on the hallux being reduced to where it registers no impression or only a minute impression, and therefore assigned to the blanket ichnogenus Avipeda following the synonymy of Vialov (1966), and Scrivner (1984). Upon further scrutiny, the size and morphology of Gruipeda diabloensis closely resembles footprints of the modern calidridine least sandpiper Calidris minutilla.

CLASS MAMMALIPEDIA Vialov, 1966

ORDER CARNIVORIPEDIDA Vialov, 1966

MORPHOFAMILY MUSTELIPEDIDAE ichnofam. nov.

Ichnogenus Mustelidichnum Aramayo and Manera de Bianco, 1987

Mustelidichnum Aramayo and Manera de Bianco, 1987: 535, 544 Figures 4a, 4b.

Type ichnospecies.- Mustelidichnum enigmaticum Aramayo and Manera de Bianco, 1987: 535, 544 Figures 4a, 4b, late Pleistocene (Lujanian), Argentina.

Emended diagnosis (based on Aramayo and Manera de Bianco, 1987).- Intermediate-size plantigrade to digitigrade obligate quadruped pentadactyl footprint exhibiting five sharply-clawed digits, each with a spheroidal to ovoidal digital pad. There is no separation between claw and digital pad giving each pad a characteristic pointed appearance. Manus typically smaller than pes. Both manus and pes roundish, slightly wider than long. Pes partially webbed, with webbing impressed between the central digits. Digital pads elongated and crowded, aligned in a conspicuous 1-3-1 spacing, with outer digits I and V separated slightly from central digits II-IV. This asymmetric placement of digits and the presence of a chevron-shaped interdigital pad are diagnostic characteristics of the carnivorian family Mustelidae. The interdigital pad impression may be subquadrangular, commonly deeply-lobed, fused, and continuous.

Ichnospecies Mustelidichnum vallecitoensis ichnosp.

nov.

V6280

(Figure 6)

photo of Mustelidichnum vallecitoensis
Figure 6. Mustelidichnum vallecitoensis (ichnosp. nov.): isolated natural mold impression of a left pes paw-print (V6280) of a musteloid in hardened claystone from Camel Ridge. Track horizon 9. Length of digit III is 2.2 cm for scale.

Holotype.- ABDSP 1745/V6280 (Figure 6). Described specimen is an isolated and undistorted left pes musteloid footprint impression preserved on what used to be a moist subaerially-exposed micaceous silty claystone bedding plane surface. Specimen is accessioned into the fossil vertebrate collections of the SRC.

Additional material.- Musteloid footprint impressions that compare favorably to V6280 have not been found.

Etymology.- In reference to sedimentary exposures of the Vallecito Badlands above the Palm Spring Formation that yield many significant vertebrate fossils.

Diagnosis.- Type specimen is preserved as a natural mold(concave epirelief) on ripplebedded, very fine-grained micaceous claystone. Represents a left pes paw-print of an intermediate-size plantigrade to digitigrade musteloid trackmaker. The paw-print exhibits five well-developed digits (I-V), each with a spheroidal to ovoidal digital pad. Central digits (II, III, and IV) are parallel; outer digits (I and V) are offset and angle slightly outward. Arrangement of the digits forms a single semicircular arc in front of the interdigital pad. Digital pad impressions are of equal or similar size, with digit I subordinate to the central digits II-IV. Each digit possesses a non-rectractile acuminate claw that may or may not register. There is no separation between claw and digit. Claw marks indistinct, and may give each digit an elongated, pointed appearance. Webbing normally present, especially in the pes, impressed between digits. The interdigital pad is large, deeply lobed, and asymmetric with an elongated proximal (metatarsal) heel. The anterior of the interdigital pad is chevron-shaped, longer than wide.

Dimensions.- Type specimen (left pes): overall print length 11.5 cm; overall print breadth 8.5 cm. Length of digits: I, 2.3 cm; II, 2.0 cm; III, 2.2 cm; IV, 2.7 cm; and V, 2.0 cm. Breadth of digits: I, 1.4 cm; II, 1.3 cm; III, 1.3 cm; IV, 1.5 cm; and V, 1.5 cm. Interdigital pad length, 7.7 cm; interdigital pad breadth, 6.5 cm.

Locality.- Camel Ridge (Anza-Borrego Zone 35), Arroyo Seco del Diablo, Vallecito-Fish Creek Basin, approximately 34 km east of Canebrake, California. The exact locality, ABDSP 1745, is on file at the SRC.

Horizon.- Fluvial, thin-bedded, micaceous silty claystone interbed of the Ocotillo Formation. Track horizon 9.

Age.- Late Pliocene (Blancan III).

Possible affinity of the trackmaker.- The morphological attributes of the ABDSP 1745 ichnotrack not only resembles those made by an aquatic mustelid but represents the first unequivocal track evidence ever reported in California. Although somewhat speculative, the only likely candidate recognized from the Vallecito-Fish Creek Basin may be the small-clawed river otter Satherium piscinarium (Remeika et al., 1995). S. piscinarium is well-represented in North America during the Blancan (Kurtén and Anderson, 1980) and may be expected in the Camel Ridge lacustrine deposits although its body-fossil record has not so far been reported. From the positive evidence thus far gathered, S. piscinarium is most likely to be the trackmaker.

MORPHOFAMILY CANIPEDIDAE ichnofam. nov.

Ichnogenus Chelipus Sarjeant and Langston, 1994

Chelipus Sarjeant and Langston, 1994: 28-29; Remeika, 1999: 42-43, 63.

Type ichnospecies.- Chelipus gracilis Vialov, 1965 (= Bestiopeda gracilis Vialov, 1965: 113; Vialov, 1966: 134-135, 202, Figure 2), Miocene (Burdigalian), Ukraine.

Other ichnospecies.- Chelipus therates Remeika, 1999: 42-43, Figure 8, Pliocene (Blancan), ABDSP, San Diego County, California; Pehuencoichnum gracilis Aramayo and Manera de Bianco, 1987: 534-535 Figures 3a, 3b, late Pleistocene (Lujanian), Argentina.

Emended diagnosis.- The morphofamily Canipedidae differs from the blanket sister taxon Carnivoripedidae of Vialov (1966), embracing only small plantigrade to digitigrade obligate quadruped tetradactyl canoid footprints exhibiting four digits (II-V), each with a spheroidal to ovoidal digital pad, sharp permanently extended claws are present and normally inpressed. Central digits (III and IV) parallel and symmetrical, outer digits (II and V) proximally divergent at angles of less than 20 degrees.

Discussion.- Sarjeant and Langston (1994) introduced Chelipus as a new ichnogenus defined by footprints in which the claws are permanently extended, specifically in footprints of canoids. This distinction follows Sarjeant and Langston's (1994) division of Vialov's (1965, 1966) blanket ichnogenus Bestiopeda. Ichnotracks of Pehuencoichnum gracilis (Aramayo and Manera de Bianco, 1987: 534-535, 543 Figures 3a, 3b) reflect a footprint structure strikingly like that of a canoid rather than a feloid as originally assigned, and are certainly referable to Chelipus as a member of this ichnogenus.Footprints assigned to the ichnogenus Chelipus are gracile in size and morphology, barely within the lower limits of the modern juvenile Canis lupus (wolf) track dimensions, but differ in no significant way from modern footprints of a moderate-size coyote (Canis latrans). Registration of conspicuous claw marks and a triangular shaped interdigital pad are diagnostic characteristics of the carnivorian family Canidae and distinguishes this ichnogenus from feloid footprints. Footprint size and morphology of obviously synapomorphic characteristics shared with extant canoid carnivorous trackmakers, especially Canis latrans (coyote), suggests attribution to the ichnogenus Chelipus is very reasonable.

Ichnospecies Chelipus therates Remeika, 1999

V6276, V6276A, V6277, V6277A, V6278, V6278A, V6279

(Figure 7)
photograph of a well-preserved ceiling cast set of canoid tracks in sandstone from Fish Creek Canyon

Figure 7. Photograph of a well-preserved ceiling cast set of canoid tracks in sandstone from Fish Creek Canyon. Track horizon 4. Chelipus therates Remeika, 1999. Note larger load-bearing left manus footprint (V6276) and its relationship to the smaller left pes footprint (V6277). For scale, the manus is 6.4 cm in length and 5.9 cm in width.

Canipeda sp. cf. Borophagus sp. (bone-eating dog track) Remeika et al., 1995: 90.

Canipeda sp. cf. Borophagus sp. Remeika, 1995: 24.

Chelipus therates, a likely canoid Remeika, 1999: 42-43, Figure 8, 63.

Holotype.- Left manus (ABDSP 1732/V6276) and a left pes (ABDSP 1732/V6277) (Figure 7). Footprint impressions represent an undistorted set of ichnotracks preserved as sandstone ceiling casts on the underside of a massive channel sandstone strike ridge panel. Plaster cast replicas (V6276A and V6277A) are accessioned into the fossil vertebrate collections of the SRC. Original specimens remain uncollected in situ.

Additional material.- Paratypes: one manus impression ABDSP 1731/V6278 preserved as an oblique sandstone ceiling cast. This specimen outcrops on strike with the holotype, exhibiting four claw marks registered in the footprint impression. A plaster cast replica (V6278A) is accessioned into the SRC. A second manus impression ABDSP 1736/V6279 is preserved as a sandstone ceiling cast (Figure 8). Due to the nature of exposure, it remains uncollected in situ.

Etymology.- Greek chele, claw; pous, foot; therates, hunter; in reference to a foraging carnivore that wanders about seeking food, hence "claw-footed hunter".

Well-preserved ceiling cast impression of an isolated track of Chelipus therates Remeika
Figure 8. Well-preserved ceiling cast impression of an isolated track of Chelipus therates Remeika, 1999 in claystone from Fish Creek Canyon. Track horizon 4. Note triangular-shaped interdigital pad configuration and presence of claw marks. Scale: same as used in Figure 7.

Diagnosis.- Type specimens are preserved in convex hyporelief, and represent manus and pes paw-prints of an intermediate-size digitigrade canoid trackmaker. The manus is noticeably larger than the pes. Paw-prints exhibit four well-developed digits (II-V), each with an elongate (long axis) spheroidal to ovoidal digital pad. Central digits (III and IV) are thick, exhibit bilateral symmetry, and give rise to a prominent non-retractile acuminate claw, fully extended. On the
manus, only the tips of claws are impressed dependent on the substrate. Outer digits (II and V) angle slightly outward, are also thick, and possess non-retractile acuminate claws that may or may not register. Arrangement of the digits forms a single semicircular arc in front of the sole and heel pad. Digital pad impressions are of equal or similar size, longer than wide, and closely-spaced. Central digits may be smaller than outer digits. The interdigital pad is large, deeply lobed, and equilateral with one rounded lobe centered anteriorly, and two subordinate rounded lobes posteriorly positioned on either side of, and laterally stepped-down from, the central lobe. The overall pad shape is triangular. On the manus (load-bearing), the interdigital pad is large and crescent-shaped. On the pes, it is typically narrow or ovoid with a lack of space between digits and anterior edge. The leading edge tends to be convex. The overall shape of the manus and pes is rectangular, longer than wide.

Dimensions.- Holotype: left manus (V6276): overall print length 6.4 cm; overall print breadth 5.9 cm. Length of digits: II, 2.4 cm; III, 2.6 cm; IV, 2.6 cm; V, 2.5 cm. Breadth of digits: II, 1.5 cm; III, 1.5 cm; IV, 1.5 cm; V, 1.7 cm. Interdigital pad length, 2.5 cm; interdigital pad breadth, 3.3 cm. Observed claw length (manus): II, not present; III, 1.0 cm; IV, 0.7 cm; V, not present. Holotype: left pes (V6277): overall print length 6.0 cm; overall print breadth 4.7 cm. Length of digits: II, 1.9 cm; III, 2.2 cm; IV, 2.3 cm; V, 1.7. Breadth of digits: II, 1.4 cm; III, 1.2 cm; IV, 1.4 cm; V, 1.3 cm. Interdigital pad length, 2.0 cm; interdigital pad breadth, 2.5 cm. Pes claw marks not observed. Since only one set of tracks is preserved, the intergroup distance and stride measurements are not applicable herein.

Discussion.- Canoid impressions of Chelipus therates occur as a set of ichnotracks in direct association with Lamaichnum borregoensis, Megalamaichnum albus, Pumaeichnum milleri, and Stegomastodonichnum garbanii. Footprints are definitely doglike, with manus and pes registry identical in size and morphology parameters to those of a typical contemporary western coyote (Canis latrans). While correlation with extant C. latrans may be unjustified, the close correspondence in footprint structure and measurements is too obvious to require critical argument. Therefore, the trackmaker of Chelipus therates is an extinct coyote. The manus holotype V6277 compares favorably to isolated paratypes preserved in convex hyporelief, discovered at localities ABDSP 1731, and ABDSP 1736.

Locality.- Fish Creek Canyon (Anza-Borrego Zone 29), Vallecito-Fish Creek Basin, approximately 29 km southwest of Ocotillo Wells, California. The exact locality, ABDSP 1732, is on file at the SRC.

Horizon.- Thick-bedded, fine-grained fluvio-deltaic arenite deposit of the Palm Spring Formation. Track horizon 4.

Age.- Late Pliocene (Blancan III).

Possible affinity of the trackmaker.- Coyote-like canid body-fossils are reported from the Arroyo Seco Local Fauna (Remeika et al., 1995). Since the morphological attributes of the ABDSP 1732 sample ichnotracks are nearly indistinguishable from the extant western coyote Canis latrans (Table 1), a plausible candidate trackmaker may be C. lepophagus. This extinct coyote is well-represented throughout western North America during the late Blancan-early Irvingtonian, and is the direct ancestor of Irvingtonian-Recent coyotes (Kurtén and Anderson, 1980).

Table 1. Measurements of manus and pes impressions of Chelipus therates [1] compared with modern western coyote footprint examples of Canis latrans [2] collected from Borrego Valley, California, and Mexican wolf footprint examples of Canis lupus baileyi [3] collected at the Living Desert Reserve, Palm Desert, California. ICN, ichnite; RM, right manus; LM, left manus; RP, right pes; LP, left pes; PL, print length; PB, print breadth; DL, digit length; DB, digit breadth; IPL, interdigital pad length; IPB, interdigital pad breadth. Measurements in centimeters (cm).

ICN PL PB DL II DL III DL IV DL V DB II DB III DB IV DB V IPL IPB

ABDSP 1732/V6276

LM 1

6.0 5.9 2.4 2.6 2.6 2.5 1.5 1.5 1.5 1.7 2.5 3.3

ABDSP 1732/V6277

LP 1

6.0 4.7 1.9 2.2 2.3 1.7 1.4 1.2 1.4 1.3 2.0 2.5
Canis latrans                        
LM 2 5.5 5.8 1.9 2.0 2.1 1.9 1.2 1.4 1.4 1.3 2.3 3.0
RM 2 5.5 5.7 1.9 2.1 2.1 1.9 1.1 1.4 1.3 1.3 2.3 2.9
LP 2 5.4 4.7 1.9 2.0 2.0 1.8 1.3 1.2 1.3 1.2 2.0 2.5
RP 2 5.3 4.7 1.8 2.0 2.0 1.8 1.2 1.2 1.3 1.2 2.1 2.4
Canis lupus baileyi                        
RM 3 7.3 7.4 2.6 2.7 2.5 2.1 1.7 1.6 1.6 1.3 3.2 4.2
RP 3 6.7 6.5 2.2 2.7 2.7 2.1 1.4 1.7 1.4 1.2 2.8 3.7

MORPHOFAMILY FELIPEDIDAE ichnofam. nov.

Ichnogenus Pumaeichnum Aramayo and Manera de Bianco, 1987

Pumaeichnum Aramayo and Manera de Bianco, 1987: 534;

Pumaeichnium Remeika, 1999: 42.


Type ichnospecies.- Pumaeichnum biancoi Aramayo and Manera de Bianco, 1987: 534, 543 Figures 2a, 2b, late Pleistocene (Lujanian), Argentina (=Bestiopeda bestia Vialov, 1966: 128-129, 202 Figure 1), Miocene (Budigalian), Ukraine.

Other ichnospecies.- Pumaeichnium milleri Remeika (1999: 42, Figures 6-7), Pliocene (Blancan), ABDSP, San Diego County, California.

Emended diagnosis.- The morphofamily Felipedidae differs from the blanket sister taxon Carnivoripedidae of Vialov (1966), embracing plantigrade, semi-plantigrade to digitigrade obligate quadruped tetradactyl feloid footprint impressions exhibiting four digits (II-V), each with a spheroidal to ovoidal digital pad forming a single semicircle arc in front of the interdigital pad sole and heel impressions. Digital pads are of equal or similar size. Impressions of claw tips are usually absent. Aramayo and Manera de Bianco (1987) restricted the ichnogenus Pumaeichnum as a junior synonym of the ichnogenus Bestiopeda Vialov (1965: 112; 1966: 128), emending Pumaeichnum to a specific ichnogenus that embraces only feloid footprints and trackways.

Discussion.- The morphology of the whole foot structure, as indicated by the preserved footprint impressions, makes their systematic assignment to the ichnogenus Pumaeichnum very strong. Diagnostic feloid footprint characteristics, such as arrangement of the digits and pad impressions, deeply bilobed anterior/trilobed posterior interdigital pad heel configuration, and impressions with claws normally retracted and claw tips usually absent except in the case of aberrant canid-like feloid tracks, is a trait of the carnivorian family Felidae and distinguishes footprints assigned to this ichnogenus from those of typical canoid footprints. This recognition is significant and strongly suggests a predatory feloid trackmaker, intermediate in size, based on the morphometric analysis of the footprints as compared, for example, to the existing felids Lynx rufus (western bobcat) and Felis concolor (western mountain lion).

Ichnospecies Pumaeichnum milleri Remeika, 1999

emend. Remeika, nov.

V6106, V6106A, V6282, V6282A, V6284

(Figure 9)

Pumaeichnium milleri a likely feloid Remeika, 1999: 42, Figures 6-7, 63.
well-preserved feloid right manus ceiling cast impression of Pumaeichnum milleri Remeika

Figure 9. Well-preserved feloid right manus ceiling cast impression of Pumaeichnum milleri Remeika, 1999 (V6106) in sandstone from Fish Creek Canyon. Track horizon 4. Note deeply bilobed anterior/trilobed posterior interdigital pad configuration and absence of claw marks. For scale, the manus is 6.1 cm in length and 6.3 cm in width.

Holotype.- ABDSP 1732/V6106 right manus (Figure 9), and ABDSP 1732/V6282 left pes (Figure 10) footprint impressions preserved as an undistorted set of ichnotracks on the underside of a massive channel sandstone strike ridge panel. The manus specimen is accessioned into the fossil vertebrate collections of the SRC. The pes impression remains uncollected in situ. Plaster cast replicas (V6106A and V6282A) are accessioned into the SRC.

Additional material.- Paratype ABDSP 1732/V6284 is an isolated manus footprint impression outcropping on the same sandstone panel. It remains uncollected in situ.

Etymology.- Fossil feloid footprint impressions, named in honor and memory of George J. Miller, who served as Curator of Paleontology at the IVCM.

Diagnosis.- Type specimens are preserved in convex hyporelief, and represent right manus and left pes paw-prints registered as a set of ichnotracks of a lynx-size digitigrade feloid trackmaker. The manus is noticeably larger than the pes. Paw-prints exhibit four well-developed digits (II-V), each with a spheroidal to ovoidal digital pad. Central digits (III and IV) are parallel and asymmetric; outer digits (II and V) angle slightly outward. Arrangement of the digits forms a single semicircular arc in front of the interdigital heel pad. Digital pad impressions are of equal or similar size, almost wider than long. Acuminate claws retractile; impressions of claw tips usually absent. The interdigital pad is large, deeply lobed, and equilateral especially in the pes, with two lobes anteriorly, and three lobes posteriorly. In cross-section, the central lobe II of the interdigital pad is equilateral or slightly diminished in profile when compared with lobes I and III. In longitudinal cross-section, the interdigital pad anterior heel lobes are canted higher forward and squared off in comparison to the lesser posterior heel lobes. The overall shape of the manus and pes is round or wider than long. Digits II, III, IV, and V of the manus are spread more than in the pes; manus digits II, III, and IV are imprinted deeper than digit V indicating a right manus, and that they are the principal load-bearing digits. The left pes tends to be wider than long.
Partially-preserved feloid left pes ceiling cast impression Pumaeichnum milleri Remeika
Figure 10. Partially-preserved feloid left pes ceiling cast impression of Pumaeichnum milleri Remeika, 1999 (V6282) in sandstone from Fish Creek Canyon. Track horizon 4. For scale, the pes is 4.5 cm in length and 5.5 cm in width.



Dimensions.- Holotype: right manus (V6106): overall print length 6.1 cm; overall print breadth 6.3 cm. Length of digits: II, 2.5 cm; III, 2.7 cm; IV, 2.4 cm; V, 1.6 cm. Breadth of digits: II, 1.2 cm; III, 1.2 cm; IV, 1.1 cm; V, 1.2 cm. Interdigital pad length, 2.7 cm; interdigital pad breadth 3.6 cm. Holotype: left pes (V6284): overall print length 4.5 cm; overall print breadth 5.5 cm. Length of digits: II, 1.6 cm; III, 1.4 cm; IV, indeterminate; V, 1.5 cm. Breadth of digits: II, 1.2 cm; III, 1.2 cm; IV, 1.1 cm; V, 1.0 cm. Interdigital pad length, 1.9 cm; interdigital pad breadth, 3.3 cm. Since the impressions represent only a set of ichnotracks, the intergroup distance and stride measurements are not applicable herein.

Discussion.- Feloid footprint impressions occur in direct association with ichnotracks of Lamaichnum borregoensis, Megalamaichnum albus, Chelipus therates, and Stegomastodonichnum garbanii. Footprints are definitely catlike, being larger than modern tracks of Lynx rufus (western bobcat), yet smaller in size than the ichnotrack of P. stouti and modern tracks of Felis concolor (western mountain lion).

Locality.- Fish Creek Canyon (Anza-Borrego Zone 29), Vallecito-Fish Creek Basin, approximately 29 km southwest of Ocotillo Wells, California. The exact locality, ABDSP 1732, is on file at the SRC.

Horizon.- ABDSP 1732 is a prominent thick-bedded, fine-grained arenite bed, part of a multistoried sequence of fluvio-deltaic sediments deposited by the ancestral Colorado River as the Palm Spring Formation. Track horizon 4.

Age.- Late Pliocene (Blancan III).

Possible affinity of the trackmaker.- Cranial and postcranial elements found in partial articulation are referable to the lynx-size cat Felis rexroadensis reported from the Vallecito Creek Local Fauna (Remeika et al., 1995). Due to the robusticity of the footprints, a morphometric resemblance to Lynx rufus is ruled out. Since Felis concolor is a late Pleistocene (Rancholabrean)-Recent (Holocene) cat, the reasonable candidate trackmaker may be the intermediate lynx-sized F. lacustris which is conspecific to F. rexroadensis. F. lacustris is well-represented throughout western North America during the Blancan-early Irvingtonian (Werdelin, 1985). Table 2 measurements indicate the ichnospecies P. milleri is morphometrically divided betweeen the genera Lynx and Felis yet exclusively shares a resemblance to lynxes and pumas. This is compelling evidence that F.lacustris may be the plausible candidate trackmaker.


Table 2. Measurements of manus and pes impressions of Pumaeichnum milleri [1], P. stouti [2], compared with modern western bobcat footprint examples of Lynx rufus [3, 4] collected from the coastal chaparral community of Camp Pendleton, California, and western mountain lion footprint examples of Felis concolor collected from Pine Valley [5] and Big Sur [6] California, respectively. ICN, ichnite; RM, right manus; LM, left manus; RP, right pes; LP, left pes; PL, print length; PB, print breadth; DL, digit length; DB, digit breadth; IPL, interdigital pad length; IPB, interdigital pad breadth; IND, indetermined. Measurements in centimeters (cm).
ICN PL PB DL II DL III DL IV DL V DB II DB III DB IV DB V IPL IPB

ABDSP 1732/V6106

RM 1

6.1 6.3 2.5 2.7 2.4 1.6 1.2 1.2 1.1 1.2 2.7 3.6

ABDSP 1732/V6282

LP 1

4.5 5.5 1.6 1.4 IND 1.5 1.2 1.2 1.1 1.0 1.9 3.3

ABDSP [IVCM] 866/V6285

RM 2

6.8 7.0 2.7 2.8 2.4 1.4 1.8 1.8 1.8 1.4 3.5 5.3
Lynx rufus                        
LM 3 5.0 4.5 1.7 2.0 1.9 1.6 1.1 1.0 1.0 1.1 2.0 2.8
LP 3 4.5 4.6 1.5 1.8 1.7 1.4 0.8 0.8 0.8 0.6 2.0 2.5
RM 4 5.0 4.2 1.5 1.6 1.5 1..4 0.9 0.9 0.9 0.7 2.6 3.2
RP 4 4.7 4.2 1.6 1.9 1.7 1.3 1.2 0.9 0.9 0.9 2.0 2.7
Felis concolor                        
PM 5 9.8 8.8 3.0 2.7 2.7 2.5 1.7 1.7 1.6 1.5 4.5 5.2
LM 5 9.7 8.7 3.1 3.1 3.1 2.7 1.8 1.7 1.8 1.6 4.8 6.5
RP 5 9.9 8.2 3.0 3.0 3.0 2.5 1.8 1.8 1.7 1.4 4.0 5.2
LP 5 9.9 8.9 3.0 3.1 2.8 2.5 1.7 1.8 1.6 1.4 4.2 5.2
RM 6 7.7 8.8 3.0 2.6 2.6 2.3 1.5 1.6 1.7 1.3 4.6 6.0
LM 6 7.3 8.7 3.0 IND IND 2.5 1.7 1.9 IND 1.6 4.3 6.3
RP 6 9.0 5.4 3.1 3.5 3.3 2.8 1.9 1.8 1.8 1.5 4.0 5.2
LP 6 8.1 8.2 3.0 3.0 2.9 2.7 1.7 1.9 1.9 1.4 4.0 5.0


Ichnospecies Pumaeichnum stouti ichnosp. nov.

V6285

(Figure 11)

footprints of Felis or immature Smilodon White et al., 1991: 9.

Felipeda sp. cf. ?Smilodon sp. (sabertooth track) Remeika et al., 1995: 90.

Felipeda sp. cf. Felis sp., or immature Smilodon sp. Remeika, 1995: 22.

Felipeda sp. cf. Felis sp. Remeika, 1997: I-18.

Holotype.- ABDSP 1745/V6285 (Figure 11). One isolated footprint impression of a right manus preserved as natural mold (concave epirelief) on ripplebedded, very fine-grained micaceous claystone. Specimen is accessioned into the fossil vertebrate collections of the SRC.

Additional material.- Feloid footprint impressions that compare favorably to V6285 have not been found.

Etymology.- The ichnospecies is named in honor of Betty W. Stout, for her generous and wide-
Feloid right manus natural mold impression of Pumaeichnum stouti
Figure 11. Feloid right manus natural mold impression of Pumaeichnum stouti (ichnosp. nov.) (V6285) in hardened claystone from Camel Ridge. Track horizon 9. Hammer for scale (34 cm). The manus is 6.8 cm in length and 7.0 cm in width.

ranging support of, and assistance to, the paleontologic program at ABDSP.

Diagnosis.- Type specimen is undistorted, preserved in concave epirelief, and represents a right manus paw-print of a puma-sized digitigrade feloid trackmaker. The paw-print exhibits four well-developed digits (II-V), each with a spheroidal to ovoidal digital pad. Central digits (III and IV) are parallel and asymmetric; outer digits (II and V) angle slightly outward. Arrangement of the digits form a single semicircular arc in front of the interdigital heel pad. Digital pad impressions are of equal or similar size, longer than wide. Acuminate claws may be retractile, yet claw tips are registered in the footprint impression directly joined to the anterior end of each digital pad. There is no separation between claw and pad. The interdigital pad is large, equilateral, and lobate, with two lobes anteriorly, and three lobes posteriorly. The overall shape of the pes is round or wider than long. Digits II, III, IV, and V of the manus are distinct and imprinted deeper than digit V, indicating a right manus, and that they are the principal load-bearing digits in this particular footprint impression.

Dimensions.- Right manus (V6285): overall print length 6.8 cm; overall print breadth 7.0 cm. Length of digits: II, 2.7 cm; III, 2.8 cm; IV, 2.4 cm; V, 1.4 cm. Breadth of digits: II, 1.8 cm; III, 1.8 cm; IV, 1.8 cm; V, 1.4 cm. interdigital pad length: 3.5 cm; interdigital pad breadth: 5.3 cm.

Locality.- Camel Ridge (Anza-Borrego Zone 35), Arroyo Seco del Diablo, Vallecito-Fish Creek Basin, approximately 34 km east of Canebrake, California. The exact locality, ABDSP 1745, is on file at the SRC.

Horizon.- Fluvial, thin-bedded, micaceous silty claystone interbed of the Ocotillo Formation. Track horizon 9.

Age.- Late Pliocene (Blancan III).

Possible affinity of the trackmaker.- The skeletal-fossil record in the study area includes two large felid taxa (Remeika et al., 1995), although Homotherium sp., and Smilodon gracilis morphologically could not have produced the Pumaeichnum stouti paw-print. Furthermore, diagnostic criteria described herein for other ichnospecies (Table 2) is not characteristic of P. stouti, leaving only Acinonyx (Miracinonyx) studeri (Savage, 1960) as the likely candidate trackmaker. A.(M.) studeri is an extinct puma-size cheetah that inhabited the area during the early Irvingtonian (Jefferson and Tejada-Flores, 1995). Its range into the late Blancan III represents the earliest record of cheetah in the Pliocene of California. When taken into account, this is compelling evidence for the existence of a new ichnospecies.

ORDER PERISSODACTIPEDIDA Vialov, 1966

MORPHOFAMILY HIPPIPEDIDAE Vialov, 1966

Ichnogenus Hippipeda Vialov, 1966

Hippipeda Remeika, 1999: 43-44; Sarjeant and Reynolds, 1999: 14-15.

Type ichnospecies.- Hippipeda aurelianis Vialov, 1966: 137-138, 203, Figures 1-2, Neogene, Ukraine.

Other ichnospecies.- Hippipeda sp. A Scrivner, 1984: 173-175, Figure 38; Scrivner and Bottjer, 1986: 302, Figure 6A, late Miocene (Hemphillian), Death Valley, California. Hippipeda sp. B Scrivner, 1984: 173, 176-177, Figure 39; Scrivner and Bottjer, 1986: 303, Figure 6B, late Miocene (Hemphillian), Death Valley, California. Hippipeda sp. C Scrivner, 1984: 173, 178-179, Figure 40; Scrivner and Bottjer, 1986: 303-304, Figure 6C, late Miocene (Hemphillian), Death Valley, California. Hippipeda araiochelata Sarjeant and Reynolds, 1999: 15-16, Plate 8, Figures 1-3, Figure 22, Plate 9, Figures 1-2, Miocene (Barstovian), San Bernardino County, California. Hippipeda absidata Sarjeant and Reynolds, 1999: 16, Plate 1, Figure 3, Plate 8, Figure 4, Figure 23, late Miocene (Hemphillian), Death Valley, California. Hippipeda gyripeza Sarjeant and Reynolds, 1999: 16-17, Plate 8, Figure 4, Figure 24, late Miocene (Hemphillian), Death Valley, California. Hippipeda downsi Remeika, 1999: 43-44, Figure 9, Pliocene (Blancan), ABDSP, San Diego County, California.

Diagnosis.- As for ichnospecies; monotypic.

Ichnospecies Hippipeda downsi Remeika, 1999

V6283

(Figure 12)

Hippipeda sp. cf. Dinohippus sp., (Pliocene horse track) Remeika et al., 1995: 90.

Hippipeda sp. cf. Dinohippus sp. Remeika, 1995: 24.

Hippipeda downsi Remeika, 1999: 43-44, Figure 9, 63.

Holotype.- ABDSP 1730/V6283 (Figure 12) is an undistorted manus hoofprint mold preserved on what used to be moist yet cohesive well-sorted micaceous sands and silts. Specimen remains uncollected in situ. A plaster cast replica (V6283A) is accessioned into the fossil vertebrate collections of the SRC.

Additional material.- Paratypes: V6270, V6271, and V6272 remain uncollected in situ. Plaster cast replicas V6270A, V6271A, and V6272A are accessioned into the SRC.

Etymology.- Fossil monodactyl equoid footprint impressions, specifically named to the honor and memory of vertebrate paleontologist Ted Downs, Chief Curator Emeritus, Los Angeles County Museum of Natural History, for his outstanding contributions to southern California paleontology.

undistorted well-preserved equoid manus hoofpring mold impression of Hippipeda downsi Remeika
Figure 12. Undistorted well-preserved equoid manus hoofprint mold impression of Hippipeda downsi Remeika, 1999 (V6283) in clayey siltstone from Fish Creek Wash. Track horizon 1. For scale, the manus is 6.2 cm in length and 12.0 cm in width.

Diagnosis.- Type specimen preserved in concave epirelief, of a digitigrade obligate quadruped equoid manus footprint, ovoidal to rectangular-shaped, distinguished by a single central digital pad toe (III) impression (mesaxonic). There is no evidence of lateral toe (II and IV) support impressions. Anteriorly, the pad is bordered by a strongly curved toe, white line, and hoofwall preserved in the relatively moist but compactible sands prior to hardening. The sole is well-pronounced, concaved downward to the bar which defines the posterior ends of the pad. The sole surrounds a nondescript V-shaped frog that is subtly expressed or absent. The overall shape of the manus print is, in most examples, wider than long. The prevalence, size, and morphology of the footprint impression along with others strongly suggest that equids are the responsible trackmakers. Observations of similarly-sized living domestic equid trackmakers leaving behind unshod imprints made in moist sand are nearly identical in size and morphology to V6283.

Dimensions.- Overall print length 6.2 cm; overall print breadth 12.0 cm.

Discussion.- Even though equid body fossils are a common constituent throughout the local vertebrate faunas, evidence of their footprints has been noticeably absent. This is problematic because the osteological record of the western Vallecito-Fish Creek Basin indicates that monodactyl equoid ichnotracks should be more common than those of llamoids, for example. ABDSP 1730 is the first and only documented equoid tracksite in the Colorado Desert at this time. The abundance of equoid ichnotracks in the stratum level seemed at first glance difficult to reconcile, originally appearing as physically induced soft-sediment deformation structures superficially resembling a ripplebedded horizon. Upon closer scrutiny, the structures were recognized as a fortuitous bedding-plane exposure of laterally-occurring, closely-spaced monodactyl ichnotracks confirming a biogenic origin for the deformation. Ichnotrack abundance is great, ranging in size from adult to juvenile, and distribution of footprints throughout this thoroughly trampled stratigraphic horizon will prove to be an untapped resource, providing significant sedimentological and paleoecological data. Adjacent beds, above and below, lack such deformation.

Locality.- Fish Creek Wash (Anza-Borrego Zone 28), Vallecito-Fish Creek Basin, approximately 30 km southwest of Ocotillo Wells, California. The exact locality, ABDSP 1730, is on file at the SRC.

Horizon.- Locally-derived fluvial sheet-flood deposit of the Ocotillo Formation. Track horizon 1.

Age.- Late Pliocene (Blancan III).

Possible affinity of the trackmaker.- The morphological attributes of the ABDSP 1730 ichnotracks suggest they belong to a single monodactyl trackmaker. Traditionally, two valid pliohippine candidates that shared synampomorphies are recognized from Anza-Borrego: Dinohippus sp., and the dolichohippine Equus simplicidens. The structurally primitive Dinohippus sp. is a monotypic taxon known primarily from the Hemphillian. However, in a revision of equids from Anza-Borrego, Downs and Miller (1994) extended its morphological/stratigraphic range to the late Blancan IV, based on diagnostic craniodental elements found below and above ABDSP 1730. With some hesitation, the relictual occurrence of Dinohippus sp., if appropriately diagnosed, seems satisfactory to include it as the likely candidate trackmaker. On the other hand, Equus simplicidens is exclusively a Blancan taxon yet due to an absence of cranial and postcranial material in the study area, its candidacy as a plausible trackmaker is difficult to make at this time.

ORDER ARTIODACTIPEDIDA Vialov, 1966

MORPHOFAMILY PECORIPEDIDAE Remeika et al., 1995

Ichnogenus Lamaichnum Aramayo and Manera de Bianco, 1987

Lamaichnum Aramayo and Manera de Bianco, 1987: 535-536; Sarjeant and Reynolds, 1999: 6.

Lamaichnium Sarjeant and Langston, 1994: 44-45; Remeika, 1999: 41-42.

Type ichnospecies.- Lamaichnum guanicoe Aramayo and Manera de Bianco, 1987: 535-536, Figures 5a, 5b, late Pleistocene (Lujanian), Argentina.

Other ichnospecies.- Lamaichnum marcopodum Sarjeant and Reynolds, 1999: 6-7, Plate 1, Figures 1-2, Figures 5-6, Miocene (Clarendonian), Inyo County, California. Lamaichnum alfi Sarjeant and Reynolds, 1999: 7-8, Plates 2-3, Figures 7-9, Miocene (Barstovian), San Bernardino County, California. Lamaichnum etoromorphum Sarjeant and Reynolds, 1999: 8-9, Plate 5, Figures 1-4, Figures 12-13, Miocene (Hemphillian), Death Valley, California. Lamaichnum obliquiclavum Sarjeant and Reynolds, 1999: 9-10, Plate 4, Figures 1-4, Figures 10-11, late Miocene (Hemphillian), Clark County, Nevada. Lamaichnium borregoensis Remeika, 1999: 41-42, Figures 3-5, Pliocene (Blancan), ABDSP, San Diego County, California.

Emended diagnosis (based on Sarjeant and Langston, 1994: 44; Sarjeant and Reynolds, 1999: 6).- Digitigrade obligate quadruped artiodactyl footprints of a small to moderate-size llamoid, showing the presence of digital cushions below the medial and distal phalanges. Footprints have an oval to rounded-rectangular shape, with two hooves in both manus and pes. Manus and pes of closely similar form. The medial (III) and lateral (IV) hoofprints have parallel axes that are paraxonic, with a narrow, linear interdigital crestline, the apices always directed forward. The medial and lateral hooves are mirror images in outline. Hoofprints widest near the heel, but taper only to a minor degree between the heel and the apex; heel rounded, apex rounded for forming a broad parabolic curve.

Discussion.- Aramayo and Manera de Bianco (1987) described the original generic and specific diagnosis of hoofprints of the type ichnospecies Lamaichnum guanicoe entirely on cloven-hoofed footprints typical of the trackmaker Lama guanicoe (guanaco). Hence, Lamaichnum is a valid ichnogenus, intended to embrace didactyl artiodactyl hoofprints and trackways made specifically by gracile llamoid trackmakers. This ichnogenus differs in its smaller size and morphology from Megalamaichnum Aramayo and Manera de Bianco (1987: 536-537) which embraces more robust didactyl llamoid hoofprints and trackways.

Ichnospecies Lamaichnum borregoensis Remeika, 1999

emend. Remeika, nov.

V4945, V4945A, V6105, V6274, V6274A, V6275, V6286, V6286A, V6287, V6287A

(Figure 13)

artiodactyl tracks Miller et al., 1982a: poster session; 1982b: unpaginated.

llama Hemiauchenia sp. Stout and Remeika, 1991: 9.

Pecoripeda sp. cf. Camelops sp. Stout and Remeika, 1991: 9; Remeika, 1995: 99.

trackways of Camelops White et al., 1991: 10.

Pecoripeda sp. cf. Hemiauchenia sp. (llama track) Remeika et al., 1995: 91.

Pecoripeda sp. cf. Camelops sp. (camel track) Remeika, 1995: 91.

Pecoripeda sp. cf. Camelops huerfanensis (cameloid footprints) Remeika, 1995: 37; Remeika, 1997b: IV-10.

Pecoripeda sp. cf. Hemiauchenia sp. Remeika, 1995: 24.

Pecoripeda Remeika, 1997: I-18.

Lamaichnium borregoensis Remeika, 1999: 41-42, Figures 4-5, 63.

Holotype.- ABDSP [IVCM] 866/V4945 (Figure 13) of an isolated right manus footprint preserved as natural mold impression (concave epirelief) on ripplebedded, very fine-grained micaceous claystone. Original specimen was accessioned into the IVCM. At present, its whereabouts is unknown. A plaster cast replica (V4945A) is accessioned into the fossil vertebrate collections of the SRC.

Additional material.- Paratypes: ABDSP 1745/V6105 (Figure 14), and V6275 accessioned into the fossil vertebrate collections of the SRC. Additional specimens V6274 (left pes), V6286 (right pes), and V6287 (right manus) remain uncollected in situ. Plaster cast replicas (V6274A, V6286A, and V6287A) are accessioned into the SRC.
Well-preserved llamoid right manus footprint natural mold impression of Lamaichnum borregoensis

Figure 13. Well-preserved llamoid right manus footprint natural mold impression of Lamaichnum borregoensis Remeika, 1999 (V4945) in hardened claystone from Camel Ridge. Track horizon 9. The fracture to the left of the footprint impression is partially filled with a white-colored liquid plaster. For scale, the manus is 11.8 cm in length and 10.6 cm in width.

Etymology.- Named after the nearby desert hamlet of Borrego Springs, California.

Diagnosis.- Type specimen preserved in concave epirelief, represents a small to moderate-sized

bidigital plantigrade to digitigrade llamoid footprint exhibiting two distinct hooves (medial III and lateral IV) in the manus. Both medial and lateral hooves are nearly identical, presenting an oval to rectangular outline longer than wide. Anteriorly, the axes of the hooves are parallel or splayed outward, separated by a linear interdigital crestline that is broadest at the front, tapering to the heel. Each hoof is broadest at the heel, which is rounded and sharply parabolic in shape. Axial surface of the hoof is flat to slightly concave, tapering mildly to a claw (toe) at the apex. Apices of hoofprint directed forward. In other specimens where manus and pes are preserved in detail, hoof apices are rounded in the manus, pointed to rounded in the pes.

Dimensions.- Holotype: (left manus): overall length 11.8 cm, greatest breadth 10.6 cm. Length of medial hoof 11.5 cm, maximum breadth 5.0 cm; length of lateral hoof 11.0 cm, maximum breadth 4.7 cm. Greatest claw tip breadth 6.2 cm.

Discussion.- The holotype of Lamaichnum borregoensis is not only the original specimen but best preserved of all the majority of oval-shaped didactyl footprints discovered at Camel Ridge and nearby tracksites ABDSP 1745, 1746, and 1747. Stratigraphically older (Blancan III) ichnotracks that compare favorably to the form and dimension skeletal morphology of L. borregoensis occur at tracksites ABDSP [IVCM] 1315, ABDSP 1726, 1728, 1729, 1731, 1734, and 1741, and remain uncollected and unnumbered in situ. Stratigraphically younger (Blancan IV-V) tracksites ABDSP 1748, 1749, and 1750 also yield llamoid ichnotracks in Arroyo Tapiado. These are bracketed between two prominent volcanic ash beds. The earliest known occurrence (Blancan II) of L. borregoensis is from the transition zone between marine-deltaic sediments of the Yuha Formation and delta-plain sediments of the Palm Spring Formation in the Fish Creek Badlands (ABDSP 1726 and ABDSP 1741), whereby footprints are preserved in concave epirelief and convex hyporelief. Locally, the footprint morphology is similar to llamoid impressions discovered in the Borrego Badlands (Beckman Wash ABDSP 1733, and Inspiration Wash ABDSP 1743) below the stratigraphic Bishop Ash datum level (Remeika and Beske-Diehl, 1996), in direct association with robust cameloid footprints of Camelopichnum sp. (ichnogen. nov.) and an elephantoid trackway of Mammuthichnum sp. (ichnogen. nov.) not previously reported from Anza-Borrego. Regionally, the footprint morphology compares favorably to llamoid impressions of Lamaichnum obliquiclavum (Sarjeant and Reynolds, 1999) from the Mojave Desert, California, and to Pecoripeda (Ovipeda) ichnospecies B and/or ichnospecies C (Scrivner, 1984; Scrivner and Bottjer, 1986) documented from Death Valley National Park, California. (See Nyborg and Santucci, 1999, and Santucci and Nyborg, 1999 for resource inventory).
photgraph of a set llamoid tracks preserved as a natural mold impression in hardened claystone
Figure 14. Photograph of a set of llamoid tracks (Lamaichnum borregoensis) preserved as a natural mold impression in hardened claystone from Camel Ridge. Track horizon 9. Scale: same as used in Figure 13.

Locality.- Camel Ridge (Anza-Borrego Zone 35), Arroyo Seco del Diablo, Vallecito-Fish Creek Basin, discovered on 9 May, 1981, approximately 34 km east of Canebrake, California. The exact locality, ABDSP [IVCM] 866, is on file at the SRC.

Horizon.- Fluvial thin-bedded, micaceous silty claystone interbed of the Ocotillo Formation. Track horizon 9.

Age.- Late Pliocene (Blancan III).

Possible affinity of the trackmaker.- Lamaichnum borregoensis is the most common vertebrate ichnotaxon of the Vallecito-Fish Creek Basin. Its morphologic manus and pes parameters generally fits the skeletal metacarpus and phalanges foot reconstruction model of the extinct candidate trackmaker Hemiauchenia sp. (Stout and Remeika, 1991). Body fossils of the fossil quadrupedal artiodactyl Hemiauchenia macrocephala are common in Blancan III-V (Arroyo Seco Local Fauna)-Irvingtonian I (Vallecito Creek Local Fauna) strata of the Vallecito Badlands (Remeika et al., 1995) in close proximity to Camel Ridge, and in Irvingtonian I-II (Borrego Local Fauna) strata of the Borrego Badlands (Remeika and Jefferson, 1993). Size and footprint morphology clearly suggests it was produced by a llama using a quadrupedal gait and does not vary significantly from extant llama (Lama glama) footprint impressions (Table 3).

Table 3. Measurements of manus and pes hoof impressions of Lamaichnum borregoensis [1-6] compared with modern llama footprint examples of Lama glama collected from Borrego Valley, California [7], and from the Oak Valley Llama Ranch in Ramona, California [8]. ICN, ichnite; RM, right manus; LM, left manus; RP, right pes; LP, left pes; PL, print length; PB, print breadth; MHL, medial hoof length; MHB, medial hoof breadth; LHL, lateral hoof length; LHB, lateral hoof breadth; CTB, claw tip breadth; IND, indetermined. Measurements in centimeters (cm).
IND PL PB MHL MHB LHL LHB CTB

ABDSP [IVCM] 866/V4945

RM 1

11.8 10.6 11.5 5.0 11.0 4.7 6.2

ABDSP [IVCM] 866/V6105

RM 2

11.6 9.7 11.6 5.2 9.5 4.2 3.0

ABDSP [IVCM] 866/V6274

LP 3

12.5 9.0 12.5 4.9 11.2 4.0 7.1

ABDSP [IVCM] 866/V6275

RM 4

IND 9.0 IND 4.3 IND 3.9 3.7

ABDSP [IVCM] 866/V6286

RP 5

10.0 8.3 9.9 3.6 10.0 3.3 4.9

ABDSP [IVCM] 866/V6287

RM 6

10.5 7.9 10.5 3.1 10.6 3.0 2.5
Lama glama              
RM 7 10.2 8.3 10.2 3.5 10.1 3.3 5.1
RM 8 11.2 7.9 10.7 3.5 11.2 3.2 5.5
RP 8 10.4 6.8 10.2 3.0 10.4 3.0 3.5
LM 8 11.7 7.9 11.2 3.5 11.7 3.7 6.0
LP 8 10.4 8.0 10.4 3.0 10.3 3.3 6.0

 

 

Ichnogenus Megalamaichnum Aramayo and Manera de Bianco, 1987

Megalamaichnum Aramayo and Manera de Bianco, 1987: 536-537.

Type ichnospecies.- Megalamaichnum tulipensis Aramayo and Manera de Bianco, 1987: 536-537, 545 Figures 6a, 6b; Aramayo and Manera de Bianco, 1996: 50-51, 51 Plate 2a, 2b, 55 Figure 4.

Emended diagnosis (based on Aramayo and Manera de Bianco, 1987: 537; 1996: 50).- Digitigrade obligate quadruped artiodactyl footprints of a moderate to large-size llamoid, showing the presence of digital cushions below the medial and distal phalanges. Footprints have an oval to rounded-rectangular shape, with two hooves in both manus and pes. Manus and pes of closely similar form. The medial (III) and lateral (IV) hoofprints have parallel axes that are paraxonic, with a narrow linear interdigital crestline, the apices always directed forward. The medial and lateral hooves are mirror images in outline. Hoofprints widest near the heel, and taper to each apex; heel rounded forming a broad parabolic curve. This ichnogenus differs in its larger size and morphology from the smaller version Lamaichnum.

Discussion.- Aramayo and Manera de Bianco (1987, 1996) described the original generic and specific diagnosis of hoofprints of the type ichnospecies Megalamaichnum tulipensis entirely on large cloven-hoofed fossil footprints. Hence, Megalamaichnum is a credible ichnogenus, intended to embrace didactyl artiodactyl hoofprints and trackways made specifically by robust llamoid trackmakers, and not intended to include gracile llamoid ichnotracks typically represented by the ichnogenus Lamaichnum.

Discussion.- Aramayo and Manera de Bianco (1987, 1996) described the original generic and specific diagnosis of hoofprints of the type ichnospecies Megalamaichnum tulipensis entirely on large cloven-hoofed fossil footprints. Hence, Megalamaichnum is a credible ichnogenus, intended to embrace didactyl artiodactyl hoofprints and trackways made specifically by robust llamoid trackmakers, and not intended to include gracile llamoid ichnotracks typically represented by the ichnogenus Lamaichnum.

Ichnospecies Megalamaichnum albus ichnosp. nov.

V6288, V6289, V6290, V6291

(Figure 15)

fossil trackways of camelids Stout et al., 1987: 4.

Megatylopus Stout and Remeika, 1991: 9.

Megatylopus footprints, trackways White et al., 1991: 10.

Hemphillian-Blancan camel Megatylopus Stout and Remeika, 1991: 9.

Blancan camelopine Camelops Stout and Remeika, 1991: 9.

Pecoripeda sp. cf. Megatylopus sp. (large camel track) Remeika, 1995: 91.

Pecoripeda sp. cf. Megatylopus sp. Remeika, 1995: 24.

Megatylopus sp. cf. Blancocamelus sp. Remeika, 1995: 24.

Pecoripeda sp. cf. Blancocamelus sp. (camel track) Remeika et al., 1995: 90.

Ichnogenus Gambapes? (large artiodactyl) Remeika, 1999: 37, 41, 63.

Holotype.- ABDSP 1726/V6288 (Figure 15) of an isolated right manus footprint preserved as a natural ceiling cast impression (convex hyporelief) on a panel of marginal-marine foreshore claystone. The panel is part of a rockfall that collapsed during the 1968 M6.5 Borrego Mountain Earthquake. Original specimen remains uncollected in situ.

Additional material.- Paratypes: ABDSP 1745/V6289 (manus ceiling cast) and V6290 (pes floor mold) are isolated footprint impressions accessioned into the vertebrate collections of the SRC. An additional specimen ABDSP 1728/V6291 remains unmeasured due to the nature of outcrop, and uncollected in situ.
large llamoid track of Megalamaichnum albus
Figure 15. Large llamoid track of Megalamaichnum albus (ichnosp. nov.) (V6288) preserved as a ceiling cast in marine-deltaic claystone in Hanging Tracks Wash. Ruler for scale (15 cm). The right manus measures 18.5 cm in length and 14.5 cm in width.

 

Etymology.- Latin, albus = white. The specific epithet is in recognition of Dr. John A. White, for his numerous and significant contributions to ABDSP's vertebrate paleontology record and the systematics and anatomy of the Leporidae. John White accompanied me into Fish Creek Canyon prior to our scheduled field trip for the 1991 Society of Vertebrate Paleontology meetings when I made one of the Megalamaichnum albus tracksite discoveries.

Diagnosis.- As for ichnogenus.

Dimensions.- Holotype: (right manus): overall length 18.5 cm, greatest breadth 14.5 cm. Length of medial hoof 18.5 cm, maximum breadth 7.0 cm; length of lateral hoof 18.5 cm, maximum breadth 7.0 cm. Greatest claw tip breadth 3.0 cm.

Discussion.- The footprint morphology resembles the large llamoid impression Lamaichnum macropodum of Sarjeant and Reynolds (1999) from the Mojave Desert, and Pecoripeda (Ovipeda) ichnospecies A of Scrivner (1984), and Scrivner and Bottjer (1986) from Death Valley National Park, California. (See Nyborg and Santucci, 1999; Santucci and Nyborg, 1999 for resource inventory).

Locality.- Hanging Tracks Wash (Anza-Borrego Zone 7), North Fork of Fish Creek Wash, Vallecito-Fish Creek Basin, approximately 28 km south of Ocotillo Wells, California. The exact locality, ABDSP 1726, is on file at the SRC.

Horizon.- Finely-interstratified silty claystones of the marginal-marine Yuha Formation. The footprint horizon is bracketed between epifaunal shellhash deposits of Turritella imperialis, and an oyster-anomiid coquina dominated by Dendostrea vespertina.

Age.- Holotype: early Pliocene (Blancan II). Paratypes: V6289, V6290, and V6291, late Pliocene (Blancan III).

Possible affinity of the trackmaker.- The Blancan-Irvingtonian body-fossil record in the study area includes half-a-dozen artiodactyl taxa, including Blancocamelus sp., Camelops sp., Hemiauchenia blancoensis, H. macrocephala, Megatylopus sp., and Titanotylopus sp. (Remeika et al., 1995). Only the extinct llama Hemiauchenia blancoensis is well-represented, with skeletal remains common through the vertical-continuous section. This llama is larger than the gracile H. macrocephala. Based on a morphometric analysis of the available sample of ichnotracks, a reasonable assignment to the candidate trackmaker H. blancoensis seems appropriate. At the present time, no cameloid footprint impressions occur in the study area thus ruling out camelopines as the likely trackmakers.

ORDER PROBOSCIDIPEDIDA Remeika et al., 1995

MORPHOFAMILY GOMPHOTHERIIPEDIDAE ichnofam. nov.

Ichnogenus Stegomastodonichnum Aramayo and Manera de Bianco, 1987

Stegomastodonichnum Aramayo and Manera de Bianco, 1987: 521-522, 531 Figures 7a, 7b, 7c.

Type ichnospecies. _ Stegomastodonichnum australis Aramayo and Manera de Bianco, 1987: 521-522, 531 Figures 7a, 7b, 7c.

Diagnosis. _ The morphofamily Gomphotheriipedidae is distinguished by the presence of large, deeply-impressed plantigrade obligate quadruped footprints. The robusticity of the type specimen is large enough to have been made by a pentadactyl gomphotherioid trackmaker. Footprint is preserved in convex hyporelief, featuring a broad oblong to oval-shaped impression, apex forward, with three pronounced digits (II-IV) oriented anteriorly at the terminus. The exhibition of a tridactyl functional morphology is consistent with the predicted anatomy of extant elephantoid pes footprint impressions and is not unusual. Digital pads II-IV are equal in size and character, and nearly parallel in orientation. Dogits are robust and short, with a blunt anterior, and semi-circular in shape as suggested by imprint outline. Lateral digits I and V are indistinct and effaced, reduced as the circumference of the depression shrank when the foot was withdrawn. No claw marks present. the metatarsal pad is broad, flat, with a rounded heel along the posterior margin. The metatarsal pad is about 2.5 cm thick. The depth of imprint is 13.5 cm.

Ichnospecies Stegomastodonichnum garbanii ichnosp.

nov.

V6292

(Figure 16)

indeterminate gomphotheroid (ichnogenus Thrinaxopus ?) Remeika, 1999: 37, 38, 63.

well-preserved elephantoid ceiling cast impression of Stegomastodonichnum garbanii
Figure 16. Well-preserved elephantoid ceiling cast impression of Stegomastodonichnum garbanii (ichnosp. nov.) (V6292) in sandstone from Fish Creek Canyon. Track horizon 4. Posterior oblique view. For scale, the footprint measures 37.5 cm in length and 27.5 cm in width.

Holotype. _ ABDSP 1732/V6292 right pes (Figure 16) footprint impression preserved as an undistorted although somewhat featureless ichnotrack on the underside of a massive channel sandstone strike ridge panel alongside ichnotracks of Chelipus therates (Figure 17). The pes impression remains uncollected in situ.

Additional material.- Elephantoid footprint impressions that compare favorably to V6292 have not been found.

Etymology. _ The specific designation of the ichnospecies is named in recognition of vertebrate paleontologist Harley J. Garbani, and his wife Mary, honoring their support of paleontology in ABDSP spanning five decades.

Diagnosis. _ As for ichnogenus.

Dimensions. _ Holotype: right pes (V6292): overall print length 37.5 cm; overall print breadth 27.5 cm. Length of digits: I, indeterminate; II, 5.5 cm; III, 7.5 cm; IV, 2.5 cm; V, indeterminate. Breadth of digits: I, indeterminate; II, 7.5 cm; III, 8.4 cm; IV, 5.0 cm; V, indeterminate.
posterior oblique view of the ABDSP 1732 ceiling panel

Figure 17. Posterior oblique view of the ABDSP 1732 ceiling panel. Track horizon 4. Note set of canoid tracks of Chelipus therates (V6276 and V6277) with the inferred trackway overprinted by the large elephantoid track of Stegomastodonichnum garbanii (V6292). Also note presence of an isolated, paretially-preserved feloid track of Pumaeichnum milleri (unnumbered in situ) to the left of the canoid impressions. Scale: same as used in Figures 7 and 16.

 

Locality. _ Fish Creek Canyon (Anza-Borrego Zone 29), Vallecito-Fish Creek Basin, approximately 29 km southwest of Ocotillo Wells, California. The exact locality, ABDSP 1732, is on file at the SRC.

Horizon. _ Thick-bedded, fine-grained fluvio-deltaic arenite deposit of the Palm Spring Formation. Track horizon 4.

Age. _ Late Pliocene (Blancan III).

Possible affinity of the trackmaker. _ Although it is not possible to ascertain the identity of the trackmaker with certainty, the attributes of the isolated ABDSP 1732 track suggests it was made by an elephantid. Possible candidates that were large enough include: Stegomastodon mirificus, Cuvieronius sp., and Mammut americanum. It is possible one of these is the responsible trackmaker. The stegomastodont Stegomastodon sp., and gomphothere Cuvieronius sp., are primarily Blancan taxa; both are reported from the Vallecito Badlands (Remeika et al., 1995). Specifically, S. mirificus has been recovered from the late Blancan Verde Formation of central Arizona (Agenbroad et al., 1998). The mastodont M. americanum ranges from Blancan to Rancholabrean in age, may occur in the Vallecito Badlands (Remeika et al., 1995), and has recently been recovered in late Pleistocene sediments in Diamond Valley, Riverside County, California (Springer et al., 1999).

CONCLUSIONS

The Fish Creek Canyon Ichnofauna is a ubiquitous avian and mammaloid hoof- and footprint vertebrate assemblage recognized from the Vallecito-Fish Creek Basin. Seven morphofamilies are recognized, represented by nine ichnospecies, making it one of the most varied ichnofaunas yet discovered in the Colorado Desert. Indeed, only the ichnofauna described from the Hemphillian of Death Valley by Scrivner and Bottjer (1986) shows a comparable diversity of morphotypes.

The vertebrate ichnofauna includes:

· small ansiodactyl bird footprints and trackways of Gruipeda diabloensis that closely resemble, in size and morphology, tracks made by the modern calidridine least sandpiper Calidris minutilla, herein assigned to the emended ichnogenus Gruipeda (Remeika, 1999).

· a new aquatic musteloid, Mustelidichnum vallecitoensis, is interpreted to be the first unequivocal footprint evidence of an extinct river otter reported from the Pliocene of California.

· footprints of a typical carnivorian canoid, Chelipus therates, are interpreted to be identical in size and morphological parameters to modern-day footprints made by coyote-sized canids.

· intermediate-sized feloid footprint impressions of Pumaeichnum milleri are interpreted to be morphometrically divided between the genera Lynx and Felis yet exclusively share a close resemblance to lynxes and pumas.

· a robust footprint impression of a right manus representing the puma-sized feloid Pumaeichnum stouti (new) exhibits claw tips directly joined to the anterior end of each digital pad. This is interpreted to be the first recognized occurrence of an extinct cheetah footprint and the earliest record of cheetah in the Pliocene of California.

· abundant fossil monodactyl equoid footprint impressions are assigned the name Hippipeda downsi. Based on diagnostic craniodental elements belonging to the equid Dinohippus sp. found below and above the tracksite, the impressions are interpreted to be from this likely candidate trackmaker.

· abundant gracile artiodactyl footprints and trackways of Lamaichnum borregoensis occur
throughout the stratigraphic section. The morphologic manus and pes parameters generally fit the skeletal metacarpus and phalanges foot reconstruction model of the extinct candidate trackmaker Hemiauchenia macrocephala, body fossils of which are a common constituent of the Arroyo Seco Local Fauna in the study area (Remeika et al., 1995).

· abundant robust artiodactyl footprints and trackways of Megalamaichnum albus (new) clearly indicate a larger llamoid ichnospecies was common throughout the vertical-continuous stratigraphic section. Based on morphometric analysis, Hemiauchenia blancoensis is the reasonable candidate trackmaker, body fossils of which are also a common constituent of the Arroyo Seco Local Fauna (Remeika et al., 1995). The most common trackmakers were the llamoids, with Lamaichnum borregoensis ranking first and Megalamaichnum albus ranking second in relative abundance.

· the presence of a large, deeply-impressed footprint suggests it was made by an elephantid. Possible candidates include Stegomastodon mirificus, Cuvieronius sp., and Mammut americanum. The impression is the first recognized gomphotherioid footprint discovered in the Colorado Desert and is assigned to the new ichnospecies Stegomastodonichnum garbanii. It occurs in direct association with feloid, canoid, and llamoid tracks.

The presence and abundance of tracks throughout multiple stratigraphic levels is noteworthy, and indicates the area was frequented by a mammalian megafauna for a prolonged period of time, ranging from Blancan II-V. The abundant and well-preserved footprints occur in basin-margin strata of a vertical-continuous mixed-affinity marine-deltaic, delta-plain, and fluvial-alluvial fan depositional environments. Each stratum is a rich source of mammalian-dominated ichnocoenoses. The clarity of footprint preservation is extraordinary, preserved as positive ceiling casts on the undersides of thick, overhanging sandstone ledges, or as negative floor impressions associated with various interstratified, dessication mud drapes. The majority of trackmakers are hitherto unknown from the osteological record of the study area but are represented in the late Blancan V to early Irvingtonian I megafauna of the Vallecito Badlands (Remeika et al., 1995).

ACKNOWLEDGMENTS

I am grateful to Silvia A. Aramayo, of the Departamento de Geologia, Universidad Nac. Del Sur, Argentina, and Torrey G. Nyborg, of the Department of Geology, Kent State University, Ohio, for providing information about fossil vertebrate tracksites at their respective research localities: Aramayo, Provincia de Buenos Aires, Argentina; and Nyborg, Death Valley National Park, California. I thank District Interpretive Specialist Brian W. Cahill for his assistance and thoroughness with scanning the footprint illustrations, and Research Analyst I (Geographic Information Systems) P. I. Lydia Louise Jee who skillfully prepared the production Figures 3-17 published herein, and offered suggestions that improved the final version of the manuscript substantially. I am also indebted to State Park Ranger I Chris H. Smith for supplying the photograph for Figure 17, and to District Archeologist George T. Jefferson for assigning me with specimen numbers, and for kindly granting access to collections in his care. Unless noted, all ichnites were discovered, collected, and photographed by the author.

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