By J. R. Tamsitt, Ph.D.
Koskinodon (Buettneria) perfectus, a pre-historic denizen of Howard County, Texas.
From 1939 through 1942 efforts by governmental project
workers (WPA) provided a wealth of fossil materials from
many localities in Texas, and one of the most complete
collections of about 11,000 specimens of vertebrates was from
the Chinle (Dockum) formation of the Late Triassic in Howard
County. Remains were deposited in floodplains, ponds, lakes,
and rivers confined to a large basin that received sand, silt and
clay sediments from adjacent highlands (Fig. 1). Most quarries
were located on the ranch of Mrs. Sarah Mina Hyman and
daughters, Mrs. Otis Chalk and Mrs. Dora Roberts, 3 miles
north of Otis Chalk, Texas (Fig.2, 3).
Although paleobotanical specimens have not been reported
from the Otis Chalk quarries, of invertebrates unionid bivalves
(freshwater molluscs) were abundant (Elder, 1987). A small
crustacean of unknown affinity was found in a coprolite (fossil
feces) (Murry, 1986).
Vertebrate fossil collections from the Otis Chalk area were
initially made by E. C. Case of the University of Michigan in
1927 and by J. W. Stovall for the University of Oklahoma in
1931 (Gregory, 1972). Elder (1978) described the paleontology
and processes of fossilization in these quarries. Several hundred
acres of eroded land provided a rich source for these fossils,
which are from the Otischalkian (Carnian) land vertebrate
faunachron (Desojo and Heckert, 2004). The collection includes
fish, a small shark, small dinosaurs, dinosaur- and crocodile-
like reptiles, and amphibians (Fig.4) (Lucas et al., 1993;
Lehman and Chatterjee, 2005; Murry, 1986, 1989; Wilson,
1948). An important fish site not far from the reptile quarries
was excavated by Bob Schaeffer of the American Museum of
Natural History, New York, in 1954 and 1962. Many of these
fossils are discussed here, and a list from Lucas et al. (1993) is
given in Appendix I.
Fish faunas include both freshwater sharks and bony fish,
including lung fish and a lobe-finned fish or coelocanth
(reviewed by Huber et al., 1993; Schaeffer, 1967). Hybodontoid
(“humped tooth”) sharks (Lonchiodion humblei) were small,
reaching a length of about 6 inches (15.2 cm), and inhabited
freshwater. Lungfish (Arganodus) were 3 feet (1 m) in length
and weighed to 70 pounds (32 kg). Their comb-shaped teeth
were used as crushing plates for clams. They were probably
similar to modern lungfish and lived in underwater burrows
during dry periods until monsoons occurred. The lobe finned
fish was not determined but likely similar to the related species
from New Mexico, Chinlea sp. (Fig. 5). Among fossilized fish
was the carnivorous Turseodus, which fed on invertebrates and
other fish. Also present was the omnivore Ceratodus, which fed
on aquatic plants, worms, other invertebrates, and fish. Several
"ganoid" fishes (with armor-like scales consisting of bony
plates covered with layers of dentine and enamel) —
Lasalichthys, Cionichthys, and Synorichthys — were found in
Howard County (Gregory, 1972; Murry, 1986). Few articulated
or complete fish specimens have been found (Milner et al.,
2006), although Schaeffer (1967) described several articulated
specimens, including the type specimen of the ganoid fish
Cionichthys greeni (complete skull).
More than a dozen skulls and much of the remainder of the
skeleton of a new species of an amphibian swamp predator
were unearthed by H. J. Sawin from the Otis Chalk site.
Buettneria howardensis was described by Sawin (1944) and is
considered to be a synonym of Koskinonodon perfectus. About 2
meters long, K. perfectus was an impressive amphibian (Fig. 6).
It possessed sharp, conical teeth and most likely fed on fish and
other small aquatic life. Upward facing eye sockets (Fig. 7)
suggest that Koskinonodon was an ambush predator, waiting in
the soft mud at the bottom of ponds and attacking prey
suddenly from below. Koskinonodon represents one of the last
of the labyrinthodont amphibians, which were common
worldwide during the late Paleozoic Era but became extinct at
the end of the Triassic Period. A much smaller amphibian,
Latiscopus disjunctus, with a high, narrow cranium, was
described by Wilson (1948) and is known only from Howard
County.
Fossils discovered in Howard County and New Mexico
document for the first time that dinosaurs and their non-
dinosaur ancestors lived side by side for tens of millions of
years. Chindesaurus bryansmalli (Fig. 8) was a small, bipedal
carnivore about 3 m (10’) long and weighed 200 pounds (91 kg).
Described in 1995 by Long and Murry, a fragment of a thigh
bone (femur) was found in Howard County. Examples of Late
Triassic reptiles from Howard County are Coahomasuchus
kahleorum, Longosuchus meadi, Lucasuchus hunti, unspecified
species of the semi-aquartic Phytosauridae, and Archosauria
indet. (See complete list of fossils from the Otis Chalk quarries
in the Paleobiology Database; Lucas et al., 1993).
Coahomasuchus, Lucasuchus, and Longosuchus (Fig. 9) are
similar genera in the Family Stagonolepididae. They were
heavily armored, small to medium-sized herbivores. The head
was small relative to the large body, and distinctive in shape,
flat and blunt at the front, like the snout of a pig. Chisel-shaped
teeth were small and leaf-like. Longosuchus was found in the
Dockum Group and Coahomasuchus in the Colorado City
Formation in Howard County, north of the abandoned town of
Otis Chalk.
Among fossils recovered from the Otis Chalk quarries were
remains of Trilophosaurus buettneri (Fig. 10), described by Case
(1928) as a new species. This reptile was a herbivore and to 2.5
meters long. It had a short, unusual, heavily-built skull,
equipped with massive, broad flattened cheek teeth with sharp
shearing surfaces for cutting up tough plant material. Teeth
were absent from the premaxilla and front of the lower jaw,
which in life were probably covered with a horny beak. Elder
(1978, 1987) noted the presence of abundant coprolites at the
Trilophosaurus quarry. Trilophosaurs are known only from the
Late Triassic of North America and Europe.
Poposaurus gracilis (Fig. 11), represented by numerous
fossil remains in the Otis Chalk Quarries, belongs to an
unusualgroup of crocodile-like reptiles that includes sail-
backed, beaked, and aquatic carnivores. Fossils have been
found in Wyoming, Utah, Arizona, and Texas. Poposaurus was
an obligate biped, that is, it walked on two legs rather than
four, as in theropod dinosaurs. But as a pseudosuchian
(“false crocodile”), it is more closely related to living
crocodilians than to dinosaurs.
After excavation of the Howard County quarries 50-60
years ago, a small portion of the specimens were prepared,
studied, and published, and an even smaller number were put
on display in museums around the country, including Texas
Memorial Museum in Austin, Texas. Most were stored in
jackets (Fig. 12) at The University of Texas Vertebrate
Paleontology Laboratory in north Austin (Airhart, 2011). Now
young paleontologists are opening and studying these jacketed
specimens as part of their research, and new discoveries will
undoubtedly result from this treasure trove of Triassic life.
I am grateful to Doyle Phillips for encouraging me to write these data for Howard County and to Dr. Timothy Rowe for critically reviewing the manuscript. – July 22, 2012, Austin, Texas.
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Fig.1. Map of the Permian Basin. Howard County is indicated by the letter “H.”
Fig. 2. Yahoo map of the Otis Chalk area [1] of Howard County, Texas.
Fig. 3. Google Earth relief map of the Otis Chalk (small yellow triangle) area of Howard County. Most cleared areas are sites of producing oil wells.
Fig. 4. Triassic mural, Dinosaur Hall, Smithsonian Institution, Washington, D. C.
Fig. 5. Artist’s rendition of the coelacanth Chinlea sp., Wickipedia.
Fig. 6. Artist's rendition of Koskinodon (Buettneria) perfectus and size comparison to a human, Wilipedia.
Fig. 7. Dorsal surface of cranium of Kiskinodon (Buettneria) perfectus, American Museum of Natural History, New York.
Fig. 8. The small dinosaur Chindesaurus bryansmalli was a large predator for Triassic times (Finsley, 1999).
Fig. 9. Mounted specimen of Longosuchus meadi, Texas Memorial
Museum, Austin, and artist’s rendition (below).
Fig. 10. Mounted specimen of Trilophosaurus buettneri, Wikipedia.
Wikipedia.jpg)
Fig. 11. Artist rendition of Poposaurus, a crocodile-like predator, and size comparison to human, Wikipedia.
Fig. 12. WPA jackets stored at The University of Texas Vertebrate Paleontology Laboratory, Austin (Airhart, 2011).
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REFERENCES
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Case E. C. 1928. A cotylosaur from the Upper Triassic of western Texas. Journal of Washington Academy of Science 18:177-178.
Desojo, J.B., and A. B. Heckert. 2004. New information On the braincase and mandible of Coahomasuchus (Archosauria: Aetosauria) from the Otischalkian (Carnian) of Texas. Neues Jahrbuch für Ecologie und Palaontologie Monatscheft, pp. 605-616.
Elder, R. L. 1978. Paleontology and paleoecology of the Dockum Group, Upper Triassic, Howard County, Texas. M.S. thesis, University of Texas, Austin, Texas, 205 pp.
----------. 1987. Taphonomy and paleoecology of the Dockum Group, Howard County, Texas. Journal of the Arizona-Nevada Academy of Science, 22(1):85-94.
Finsley, C. E. 1999. Discover Texas dinosaurs. Gulf Publishing Co, Houston. x + 150 pp. Gregory, J. T. 1945. Osteology and relationships of Trilophosaurus. University of Texas Publication 4401: 273-359.
-----------. 1953. Typothorax and Desmatosuchus. Postilla, 16:1–27.
----------. 1972. Vertebrate faunas of the Dockum Group, Triassic, Eastern New Mexico and west Texas. New Mexico Geological Society, Guidebook of East-Central New Mexico. In Twenty-third Field Conference, September 1972, V. C. Kelley and F. D. Trauger, eds. Pp. 120-123.
Heckert, A.B. 2004. Late Triassic microvertebrates from the lower Chinle Group (Otischalkan-Adaminian: Carnian), southwestern U.S.A. New Mexico Museum of Natural History and Science, Bulletin 2, 170 pp.
---------- and S. G. Lucas. 1999. A new aetosaur (Reptilia: Archosauria) from the Upper Triassic of Texas and the phylogeny of aetosaurs. Journal of Vertebrate Paleontology, 19:50–68.
---------- and ----------. 2000. Taxonomy, phylogeny, biostratigraphy, biochronology, paleobiogeography, and evolution of the Late Triassic Aetosauria (Archosauria: Crurotarsi). Zentralblatt für Geologie und Paläontologie, I (11–12):1539–1587.
----------, -----------, L. F. Rinehart , M. D. Celeskey, J. A. Spielmann, and A. P. Hunt. 2010. Articulated skeletons of the aetosaur Typothorax coccinarum Cope (Archosauria: Stagonolepididae) from the Upper Triassic Bull Canyon Formation (Revueltian: early-mid Norian), eastern New Mexico, USA. Journal of Vertebrate Paleontology, 30:619-642.
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Lucas, S. G., A. P. Hunt and R. Kahle. 1993. Late Triassic Vertebrates from the Dockum Formation near Otis Chalk, Howard County, Texas. New Mexico Geological Society Guidebook, 44th Field Conference, Carlsbad Region, New Mexico and West Texas, pp. 237-244.
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Murry, P. A. 1986. Geology and paleontology of the Dockum Formation (Upper Triassic), West Texas and eastern New Mexico. Pp. 109-137. In K.Padian (ed.), The beginning of the age of dinosaurs; Faunal change across the Triassic-Jurassic boundary. Cambridge University Press, Cambridge, England.
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----------. Otis Chalk Quarry 3, TMM 31100 (Triassic of the United States).
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Sawin, H. J. 1944. Amphibians from of the Dockum Triassic Howard County, Texas. Contributions to Geology, The University of Texas, 4401: 361-399.
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Small, B. J. 1989. Aetosaurs from the Upper Triassic Dockum Formation, Post Quarry, West Texas. Pp. 301–308. In S. G. Lucas and A. P. Hunt (eds.), Dawn of the Age of Dinosaurs in the American Southwest. New Mexico Museum of Natural History, Albuquerque, New Mexico.
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Appendix I. Vertebrate Fauna from the Dockum Formation near Otis Chalk, Howard County, Texas (from Lucas et al., 1993).
Class Chondrichthyes
Lissodus sp.—One tooth.
Class Osteichthyes
Arganodus sp.—Toothplates of this lungfish.
Colobodontidae—Unidentified tooth plates cf. Turseodus sp.; corrugated scales.
Cionichthys greeni—Several partial skeletons.
Lasalichthys hillsi—One specimen.
Sinorichthys stewarti—Several partial skulls and isolated bones.
Class Amphibia
Latiscopus disjunctus—Is known only from a skull.
Buettneria perfecta—Several skulls and other bones. Apachesaurus sp.—Isolated intercentra.
Class Reptilia
Otischalkia elderae— Limb and upper jaw elements.
Trilophosaurus buettneria—More than two-thirds of the vertebrate fossils from the WPA quarries 1 and 2. Two sizes of individuals are present, and it is not certain whether the two morphs are ontogenetic members of the same species or represent distinct taxa.
Malerisaurus langstoni— a partial but poorly preserved skeleton.
Procolophonidae—Reported by Murry (1989).
"Primitive reptiles"—Jaw elements with rows of teeth. It is suspected that they are contaminants to the Otis Chalk fauna.
Poposaurus gracilis—All rauisuchian (Triassioc archosaurs) specimens from Otis Chalk probably pertain to this taxon.
Longosuchus meadei--One of the best-known aetosaurs from North America because of the abundant specimens from Otis Chalk.
New aetosaur genus—An articulated skeleton from Otis Chalk pertains to a new genus of aetosaurs , which is distinguished by its very wide dorsal paramedian scutes with radial ornamentation. This specimen exhibits a waisted carapace anterior to the pelvis and lacks raised bosses on the dorsal paramedian scutes.
Paleorhinus bransoni--at least five skulls.
Angistorhinus alticephalus—Represented by skulls and other bones.
Brachysuchus megalodon—Known from skulls, lower jaws, and other bones.
