San Bernardino County Museum Association

Special Publication VA= 93-1, MDC19? 1993 • Ashes, faults and Basins

San Bernardino County Museum Association 93-1 prepared in conjunction with the 1993 Desert Research Symposium May 21-24, 1993 9 SBCMA Spec. pubi Page 4 . /3117 Razorback Sucker (Xyrauc hen) from the Anza-Borrego Desert and the Ancestral Colorado River J.D. STEWART, Vertebrate Paleontology, Natural History Museum of Los Angeles County, Los Angeles CA 90007 MARK A ROEDER, Paleontology, San Diego Natural History Museum, P.O. Box 1390, San Diego CA 92112

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ABSTRACT The first documentation of Xyrauchen indicates that a major fluvial-tributary system of the ancestral Colorado River flowed into the Borrego Badlands during at least part of the Pleistocene period (Ocotillo formation). Xyrauchen is also present in the lower Diablo Formation in and around the San Felipe Hills.

Few fossil fresh water fishes are known from the ancestral restricted in outcrop to the Vallecito Badlands of Anza-Borrego Colorado River drainage. Xyrauchen texanus, the razorback sucker or Desert State Park ( ABDSP). To establish appropriate nomenclature humpback sucker (Fig. 1), is one of the fishes endemic to the and stratigraphic control, Remeika (1991) and Remeika and Lindsay Colorado drainage and one of the largest catostomid fishes from (1992) named the informal Diablo formation for Colorado River.

North America. The historic range of Xyrauchen is entirely within the derived fluvial sandstones deposited as part of the deltaic plain of the Colorado River drainage (Lee and others. 1980), where it is limited Colorado Rivera long the western side of the Salton Trough region of to the Colorado River and major tributaries such as the Gila and southern California. Remeika (pers. comm.) states that this Xyraurhen Green rivers. Xyrauchen is a large fish (up to 1 in) relative to other specimen (SBCM A768-1) is of early Pliocene age, demonstrating North American fresh water fishes. It was once a major food source that the large river-adapted lineage of Xyrauchen extends back more for Native Americans living along the Colorado River. Because of than three million years. manipulation of the water flow of the lower Colorado River, this fish The San Felipe Hills specimen consists of a foot long skeleton is now an endangered species in California (McGinnis, 1984). preserved inside an oval-shaped arenitic sandstone concretion. The Minkley, Hendrickson, and Bond (1986:581) mentioned that one specimen was donated to the San Bernardino County Museum by of us (MAR) had identified a "well-preserved Pleistocene fossil Ruth Coyle. According to Paul Remeika of the Anza-Borrego State Xyrauchen from the Colorado Desert west of the Salton Sea." This is Park, the lithology of the concretion appears to be from ancestral the only published reference to a fossil record of the genus to date. Colorado River-derived sediments of the Diablo formation (Pliocene) The specimen in question. SBCM A768-1, was collected by Ruth and not from the lacustrine Borrego formation. The specimen, which Coyle on the north side of the San Felipe Hills near the western is nearly complete, is being studied by Dr. Kenneth Gobalet. boundary of Imperial County and north of State Highway 78, an area California State University, Bakersfield, and Mark Roeder. Because of . originally mapped as part of the by Dibblee the completeness of the specimen, it may be possible to determine (1954). In 1991. Remeika recognized that these beds are not whether this specimen represents an earlier species of this genus, or genetically synonymous with the Palm Spring formation that is extends the range of Xyrauchen texanus to early Pliocene times.

Figure 1. Xyrauchen texanus, the razorback sucker, exhibits the unusual hump characteristic of a few of the large Colorado River fish species. SBCMA Spec. Pub!. 93-1 Page 95

Table 1. LACM specimens of Xyrauchen texanus from the Borrego Badlands elements of Xyrauchen texanus. All are from large individuals, well in excess of 50 cm standard length (comparison to LACM 43613-1). The Ocotillo formation is composed of locally-derived tACM Formation Member Specimen Elements Locality Number sediments (Remeika, 1991; Remeika and Jefferson, this volume), and probably does not represent Colorado River 4123 Ocotillo Fm 118500 fish fragments including sediments per se. These sediments more probably represent left half of autogenous a Colorado River tributary system; the fossils of large neural arch of third Xyrauchen indicate that the tributary was sizeable. The vertebra of Xyrauchen estimated age of the Ocotillo Formation in the Borrego Badlands spans approximately 0.37-1.25 Ma (Remeika and 4124 Ocotillo Fm Inspiration 130319 L quadrate, partial L Jefferson, this volume). This may or may not include some Wash Mbr operculum, neural complex, centrum, sediments of the Rancholabrean North American Land parapophysis, it 1st Mammal (NALM) Age. The Irvingtonian/Rancholabrean pectoral fin ray NALM Age boundary is not well dated or agreed upon. Estimates for the age of the boundary range from 0.2-0.55 6763 OcotiUo Fm Inspiration 130322 Neural complex, part, Ma (Lundelius and others, 1987). Regardless, the bulk of Mbr predorsal, centrum Wash the Ocotillo formation was deposited within the Age. A volcanic ash in the upper part 6775 Ocotillo Fm 135364 Neural complex Irvingtonian NALM of the Inspiration Wash member is thought to be correlated 57113 Ocotillo Fm Los Playas 130320 Neural complex with the Bishop Tuff (Remeika, 1992). A potassium/argon Mbr date is pending for that ash. The most reliable K-Ar dates and the average zircon fission-track age for the Bishop Tuff 130321 Neural complex are each approximately 0.74 Ma (hen and others, 1988). 135427 Abdominal vertebra. rib. According to Remeika (pers. comm.) some of the localities L pectoral fin ray, R half that produced the LACM specimens lie above this tuff, and autogenous neural arch some lie below. of 3rd vertebra

ACKNOWLEDGEMENTS We wish to thank Ruth Coyle for recognizing the importance of the San Felipe Hills specimen and donating Even though SBCM A768-I is of Pliocene age, Pleistocene it to the San Bernardino County Museum. Robert Reynolds (SBCM) specimens of Xyrauchen do exist. Six specimens in the Natural brought the specimen to our attention. Dr. William Minkley of History Museum of Los Angeles County (LACM) (LACM 130319, Arizona State University gave us comparative material of Xyrauchen 130320, 130321, 130322, 135364, 135467) from the Ocotillo texanus. Paul Remeika generously supplied information on the Formation are assigned to Xyrauchen texanus. srratigraphy of the Anza-Borrego Desert State Park and adjacent The osteological nomenclature employed here follows that of areas. Dr. Robert Lavenberg (LACM) gave us access to ichthyological Nelson (1948). The Weberian apparatus of Xyrauchen is most like collections in his care. Dr. John M. Harris critically read this those of the Catoitomini and Eriinyzonini, in that the neural spine of manuscript. the third vertebra does not participate in the posterior margin of the neural complex (Nelson, 1948). In Catostomus, the posterior border of REFERENCES the neural complex is very attenuate and dorso-posteriorly directed. Dibblee, T.W. Jr., 1954. Geology of the Imperical Valley region, California. Furthermore, at least two vertebral neural arches behind the neural California Division of Mines Bulletin, 170 (11,2):21-28, pl. 2: generalized complex support the neural complex in Catostomus. In Xyrauchen, geologic map of Imperial Valley region, California, scale 1 inch 6 mi. however, the supraneural is oriented directly above vertebrae one Izett. G.A., J.D. Obradovich and H.H. Mehnert, 1988. The Bishop Ash Bed through four. The neural arch of the fourth vertebra is inclined (Middle Pleistocene) and some older (Pliocene and Pleistocene) chemically slightly forward to reach the neural complex, and the fifth vertebra and mineralogically similar ash beds in California, Nevada, and Utah. U.S. extends its neural arch considerably forward to effect this contact. A Geological Survey Bulletin 1675: 37 p. large supraneural is sutured to the posterior side of the neural Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. complex, and that supraneural also has a smaller supraneural sutured Stauffer Jr., 1980. Atlas of North American freshwater fishes. Raleigh, 867 to its posterior side. Unlike the condition in Catostomus, a great deal P. Lundelius, E.L Jr., T. Downs, E.L. Lindsay, H.A. Semkin, C.S. Churcher, C.R. of the neural complex and its attached supraneural extend above the Harrington, G.E. Schultz, and S.D. Webb, 1980. The North American neural arches of vertebrae four and five. Quaremary sequence, in Cenozoic mammals of North America, M.O. The most easily identified skeletal element of Xyrauchen in Woodbume (ed). Berkeley, University of California Press:211-235. collections from the Borrego Badlands is the neural complex of the McGinnis, S.M., 1984. Freshwater fishes of California. Berkeley, University of Weberian apparatus (see Table I for complete listing). This element Califomia Press: 316 p. k and the two enlarged supraneurals of the Weberian apparatus are the Minkley, W.L., D.A. Hendrickson, and C.E. Bond, 1986. Geography and western North American freshwater fishes: description relationships to osteological basis of the conspicuous hump of Xyrauchen. Five intracontinental tectonism, in Zoogeography of North American freshwater specimens of the neural complex are represented from n four Borrego fishes, C.H. Hocutt and E.O. Wiley (eds). New York, Wiley and Sons:519- LACM collections. A fifth locality Badlands localities in the 613. produced a fragment of the modified pleural rib of the fourth centrum. None of the specimens can be distinguished from those Moyle, Peter B., 1976. Inland fishes of California. Berkeley, University of California Press: 405 p. Nelson, EM., 1948. The comparative morphology of the Weberian apparatus of the Catostomidae and its significance in systematics. Journal of 'Morphology, 83:225-251. Remeika, P., 1991. Formation status for the Diablo Red Beds; differentiating between Colorado River affinities and the Palm Spring formation, in Symposium on the scientific value of the desert; J. Rickard (ed). The Anza-Borrego Foundation, Desert Symposia. , 1992. Preliminary report on the stratigraphy and vertebrate fauna of the Middle Pleistocene Ocotillo formation, Borrego Badlands, Anza-Borrego Desert State Park, California. Abstracts of Proceedings, 6th Annual Mojave Desert Quaternary Research Symposium, San Bernardino County Museum Association Quarterly, 39(2):25-26. Remeika, P. and G.T. Jefferson, 1993. The Borrego local fauna: revised basin. margin stratigraphy and paleontology of the western Borrego Badlands, Anza-Borrego Desert State Park, California. this volume. Remeika, P. and L. Lindsay, 1992. Geology of Anza-Borrego: edge of creation. Dubuque, Kendall/Hunt Publ. Co., Sunbelt Publication California Desert Natural History Guide: 208 p. Smith, G.R., 1978. Biogeography of intermountain fishes, in intennontain biogeography: a symposium, K.T. Harper and J.L. Reveal (eds). Great Basin Naturalist Memoirs, 2:1-268.