ABSTRACTS OF THE SOCIETY OF VERTEBRATE PALEONTOLOGY DECEMBER MEETING AT BOSTON MODERN TECHNIQUES IN THE STUDY OF TERTIARY CONTINENTAL SEDIMENTS BY JOHN CLARK Early stratigraphic work in Tertiary formations was limited to faunal correlation and brief, macroscopic description of the sediments. During the past 20 years, various students have developed special techniques which have yielded valuable results. Most useful petrologic data are: (1) Quartz-feldspar ratios; (2) nature, amount, and factors controlling the cementing material; (3) color, provided that the factors controlling it can be determined; (4) nature of the heavy minerals; (5) gradations in maximum grain size. Special methods of sampling are necessary in order to obtain uniform results. Paleogeographic interpretation must at all times accompany faunal and petro­ logic studies. Local variation in facies is so extreme that without determination of the environment of deposition, correlation and interpretation become impossible. FUNCTION OF THE FORELEG IN AMPHIBIAN;LOCOMOTION BY F. GAYNOR EVANS Experiments with Amblystoma opacum indicate that the forelegs play a more important role in normal locomotion than is usually believed. Animals with the hind legs immobilized still showed fairly good forward locomotion accomplished by pulling with the forelegs and lateral undulations of the body. With the posterior part of the body supported off the substratum locomotion approached the normal. Immobilization of the forelegs rendered forward movement almost impossible, while immobilizing both pairs of legs prevented it in spite of violent lateral un­ dulations of the body. In normal locomotion the propulsive phase in the forelegs consists of a pulling action, produced by flexion of the various segments of the leg, while extension occurs chiefly during the recovery phase when the foot is off the ground. Some extension also occurs at the end of the propulsive phase just before the foot leaves the sub­ stratum. Experiments with Triturus granulosus show the pulling power of the foreleg is greater than supposed. The carpal joints of the Caudata are syndesmoses with the entire region very flexible because of the elastic tissue between the bones. Flexion and extension occur chiefly at two places—(1) between the forearm bones and the proximal row of carpals and (2) between the distal row of carpals and the metacarpals. The same conditions were presumably true in the Stegocephalia. The antero-internal region of the palm is the chief weight-bearing part of the hand. This also seems to have been true in the Stegocephalia as in many cases the tracks of the manus are deepest in this region. RELATIONSHIPS OF THE TRIASSIC REPTILE TRILOPHOSAURUS BY JOSEPH T. GREGORY The University of Texas has obtained an articulated skeleton and numerous other specimens of Trilophosaurus buettneri Case from the Upper Triassic Dockum (1987) Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/52/12_2/1987/3431052/BUL52_12B-1987.pdf by guest on 29 September 2021 1988 ABSTRACTS OF THE SOCIETY OP VERTEBRATE PALEONTOLOGY formation in Howard County, Texas. Important morphological features of this reptile are: edentulous premaxillaries and symphysis of the lower jaws; an average of 14 transversely elongated, three-cusped, thecodont teeth on each maxillary and dentary; vertical tooth succession which progressed regularly from front to back of jaws; large laterally directed orbits; superior temporal fenestrae; elevated quadrate recurved at its upper end like that of Diadectes and chelonians; quadrate exposed on lateral surface of skull and supported throughout its length by the unfenestrated postorbital region; braincase unossified anterior to sella turcica; tubera and basipterygoid processes deep; 7 procoelous cervical vertebrae with paired hyposphenes; long cervical ribs; 17 amphiplatyan dorsal vertebrae with thin, crescentic intercentra and low neural spines; numerous abdominal ribs; two strong sacral vertebrae; a long tail with elongate procoelous vertebrae; girdles with expanded ventral elements; limb bones slender; humerus with expanded ends and twisted shaft; femur with strong internal trochanter; feet large, pentadactyl, lizardlike, with strong compressed claws; tarsus with navicular; fifth metatarsal “hooked”. Structure of vertebrae, girdles, and limbs suggests that the animal was quadrupedal and lizardlike in body form. Adults about 2 meters long. Numerous similarities between Trilophosaurus and the diapsid reptiles are due to parallel evolution from a common protorosaurian ancestor. Trilophosaurus is provisionally referred to the Protorosauria. FISHES FROM THE DEVONIAN OF ARIZONA BY L. HUSSAKOF During the past few years, Devonian fish remains have been discovered at several localities in Arizona. The present paper is the first systematic description of this material. The specimens consist of single plates of Arthrodira, most of them of small forms, ptyctodont dental elements, and teeth of Dipterus. The present study is based on a small collection of such material made by Mr. L. F. Brady of the Museum of Northern Arizona, from the Mt. Elden formation, near Flagstaff, Arizona. On the evidence of the fishes, the age of the fish-bearing strata of this formation appears to be early Upper Devonian. Among the Arthrodira studied are a few fragmentary plates of a Dinichthys of medium size, ornamented with small, occasionally stellate, tubercules; and a new species of Coccosteus, represented by isolated, single plates from different parts of the body. The ventral armor of this Coccosteus was reconstructed. It presents an unusual feature in having the posterior ventrolateral plates united medianly in almost a straight line, not by overlap flanges. Ptyctodont dental elements are comparatively numerous, most of them forms with a very narrow tritor preceded by a trenchant margin. A new species of Ptyctodus is described. NEW PYCNODONT FISH FROM THE UPPER CRETACEOUS OF ARKANSAS BY L. HUSSAKOF The species is described from two nearly complete mandibulars from the Marl- brook marl (Upper Cretaceous) of Arkansas. The principal teeth consist of a single series of narrow elliptical teeth, characteristic of the genus Anomoeodus. The two specimens are both right mandibulars, from two different fishes. They show that variation occurs within the same species in the row of very small teeth in Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/52/12_2/1987/3431052/BUL52_12B-1987.pdf by guest on 29 September 2021 ABSTRACTS 1989 the symphyseal line: in one specimen there is a single row of very small teeth; in the other there is, beside this row, a second, more irregular series of somewhat larger teeth. This pycnodont occurs along with shark teeth of various species, and teleostean bones and teeth, among the latter being large, slender laniary teeth of Enchodus. This fauna of large fishes indicates open-sea conditions; and the presence of two teeth of a trigger fish (Balistidae) indicates a warm sea as the habitat of these pycnodont fishes. Specimens in the possession of their collector, Mr. C. M. Barber, Hot Springs, Arkansas. PALEOPSEPHURUS WILSONI, A NEW POLYODONTID FISH FROM THE UPPER CRETACEOUS OF MONTANA, WITH A DISCUSSION OF ALLIED FISH, LIVING AND FOSSIL BY ARCHIE MACALPIN The osteology of P. Wilsoni, n. gen., n. sp. is described and figured. Many com­ parisons are made between its structures and the supposed homologues of modem and fossil fish, especially of living paddlefish and sturgeons and of Crossopholis magnicaudatus (the only other known fossil paddlefish) from the Eocene. The material from the University of Michigan collections consists of three close-lying individuals showing (1) a well-preserved head with jaws, branchial and hyoid arches, pectoral girdle, pectoral fins, and some minute denticles; (2) part of a caudal region; (3) part of a shoulder girdle and pectoral fin. The species has a long rostrum, fenestrated cranial roof skeleton with numerous occipital plates, and a strong parasphenoid. The mouth apparatus consists of a sturdy, posteriorly directed hyomandibular, a pterygoid with an ectopterygoid process meeting a similar process from the maxillary, a quadratojugal, a maxillary and a dentary joining anteriorly with their fellows, a prearticular, and possibly several thin palatines. The strong dermal shoulder girdle has an interclavicle. Pectoral fin rays are distally segmented, not dichotomous. The trunk is covered with spinous denticles, 0.20 cm to 0.25 cm long, not in contact. Caudal fulcra and caudal oat­ shaped scutes are present. A macroscopic comparison of polyodontid squamation is made. Special attention is given to rostral and body sizes and jaw and occipital musculature with reference to feeding habits. Several undescribed features of Polyodon and Psephurus are treated. Among the suggestions offered are that (1) recent polyodontids have evolved from a line of more highly ossified ancestors, probably through some unknown palaeoniscid; (2) there is a quadratojugal in Paleopsephurus, Psephurus, and some sturgeons that appears to be homologous to that bone so called in the rhipidistians and lower Palaeoniscidae; (3) Pholidurus disjectus be removed from the family Polyodontidae; (4) the mouth of P. Wilsoni was protrusible; and (5) the length of the rostrum in comparison to the total body length exhibited by modern paddlefish had already been attained in the family by Upper Cretaceous time. ANALYSIS OF MBRYCOIDODON SKULLS BY FRED B PHLEGER, JR. One hundred