Larry F. Rinehart

A STATISTICAL ANALYSIS OF A GROWTH SERIES OF THE PERMIAN NECTRIDEAN DIPLOCAULUS MAGNICORNIS SHOWING TWO-STAGE ONTOGENY

Abstract We use probability plots to compare metric data for a growth series of the Permian nectridean Diplocaulus magnicornis Cope to a normal (Gaussian) probability distribution function and demonstrate that the ontogeny of Diplocaulus is not a single continuous process. The plots are bimodal, revealing a population of small, ontogenetically young animals whose growth is governed by a distinct process. This population, which comprises ∼20% of the growth series, is not evident in allometric studies. These young animals have a mean mid-line skull length of ∼21 mm, and their orbits are relatively larger, and rounder, than the orbits of the older animals, whose mean skull length is ∼94 mm. Although there is no evidence of lissamphibian-type metamorphosis in the Nectridea, the probability plots clearly demonstrate a two-stage ontogeny, best described as an ontogenetic morphological saltation. This saltation may have been an alternative strategy to the metamorphic heterochrony found in lissamphibians and their relatives.

Furculae in the Late Triassic theropod dinosaurCoelophysis bauri

Furculae have been identified in many dinosaurs and are synapomorphic in some clades (e.g., dromaeosaurids). All coelophysid dinosaurs exceptCoelophysis bauri have been shown to possess furculae. To date, the oldest well-documented furculae have been those of the Early Jurassic coelophysids,Coelophysis kayentakatae andCoelophysis rhodesiensis. The confirmation of furculae in Apachean-agedC. bauri further documents appearance of these elements in the Late Triassic and shows that furculae are synapomorphic in the Coelophysidae. A total of five furculae have been found in New Mexico Museum of Natural History’s (NMMNH) Ghost Ranch, New Mexico Whitaker Quarry block C-8-82. We describe three furculae in articulated juvenile skeletons; two that are missing fragments but are nearly complete, and one apparently complete, a small fragment of a furcula associated with an adultC. bauri, and one complete but isolated furcula. We access the morphology and allometry of the scapulocoracoid and furcula and show that they grow, at least in juveniles, in isometry with the humerus. The furcula ofC. bauri has a widely opened U shape that subtends an angle of ∼ 120°. All the furculae have groove-like epicleidial facets at the distal ends of the rami and some possess a small centrally located hypocleideal process. We reconstruct the complete Shoulder girdle ofC. bauri with proper spacing and angles between the elements and find that the coracoids are very close together under the center of the furcula.KurzfassungFurculae wurden in vielen Dinosauriern gefunden und sind in einigen Gruppen synapomorph (z.B. Dromaeosauridae). Furculae wurden in allen Coelophysiden nachgewiesen, mit der Ausnahme vonCoelophysis bauri. Die ältesten gut dokumentierten Furculae bei Theropoden waren bisher jene der unterjurassischen CoelophysidenCoelophysis kayentakatae undCoelophysis rhodesiensis. Die Bestätigung der Präsenz von Furculae inCoelophysis bauri, mit einem Apachium-Alter, beweist weiter den Ursprung dieses Elementes in der späten Trias und zeigt, dass Furculae für Coelophysiden synapomorph sind. Insgesamt wurden fünf Furculae in dem Block C-8-82 aus dem Ghost Ranch, New York Whitaker Quarry im New Mexico Museum of Natural History (NMMNH) gefunden. Wir beschreiben drei Furculae von artikulierten, juvenilen Exemplaren, von denen zwei fast vollständig und eine scheinbar vollständig ist, eine fragmentarische Furcula, die mit einem adulten Exemplar vonCoelophysis bauri assoziiert ist und eine vollständige, aber isolierte Furcula. Wir analysieren die Morphologie und Allometrie des Scapulocoracoids und der Furcula und zeigen, dass sie, zumindest in Jungtieren, in Bezug auf den Humerus isometrisch wachsen. Die Furcula vonC. bauri ist breit U-förmig, mit einem Winkel von ungefähr 120° zwischen den Ästen. Alle Furculae haben kleine, grubenförmige Epicleithral-Facetten an den distalen Enden der Äste und einige weisen kleine, zentral gelegene Hypocleithral-Fortsätze auf. Wir rekonstruieren den gesamten Schultergürtel vonC. bauri, mit den exakten Abständen und Winkeln zwischen den Elementen und finden, dass die Coracoide unter der Spitze der Furcula sehr eng zusammen lagen.

Lithostratigraphy, Paleontology, Biostratigraphy, and Age of the Upper Paleozoic Abo Formation Near Jemez Springs, Northern New Mexico, USA

ABSTRACT In the Jemez Springs area of Sandoval County, northern New Mexico, siliciclastic red beds of the upper Paleozoic Abo Formation are well exposed and yield fossil plants and vertebrates. The local Abo Formation section is more than 190 m thick and rests disconformably on the Upper Pennsylvanian Guadalupe Box Formation and is conformably overlain by the Lower Permian DeChelly Sandstone (Yeso Group). Abo sandstone sheets are low sinuosity river deposits, and intercalated sandstone beds and lenses represent sheet splays and minor channel fills that formed during overbank flooding. The dominant Abo lithofacies is mudstone, which represents floodplain deposits, many with calcareous paleosols. Fossils are present in three stratigraphie intervals of the lower to middle Abo Formation. All three intervals yield eupelycosaur-dominated vertebrate fossil assemblages of Coyotean age (Coyotean = late Virgilian-Wolfcampian on the North American provincial marine timescale: Lucas 2006). The lowest interval also yields the Spanish Queen Mine paleoflora of pteridosperms and conifers. Strata of the Guadalupe Box Formation disconformably below the Abo Formation contain late Virgilian fusulinids. We correlate the Abo Formation fossil assemblages in the Jemez Springs area to the Coyotean-age fossil assemblages in the upper part of the El Cobre Canyon Formation in the Arroyo del Agua area and in the Canon del Cobre in the Chama basin of northern New Mexico. This suggests a middle Wolfcampian age for the Jemez Springs area fossil assemblages, an age very close to the Pennsylvanian-Permian boundary.

Eocyclotosaurus appetolatus, a New Cyclotosaurid Amphibian from the Middle Triassic (Perovkan) Moenkopi Formation of New Mexico, U.S.A.

ABSTRACT A new species of cyclotosaurid amphibian, Eocyclotosaurus appetolatus, is based on excellent, three-dimensionally preserved material from New Mexico Museum of Natural History locality 5193 in the Middle Triassic (Perovkan) Anton Chico Member of the Moenkopi Formation near Tecolotito, New Mexico, U.S.A. The locality is a monodominant bonebed, with E. appetolatus representing the vast majority of the fossil material. E. appetolatus shares a long, narrow snout and slightly concave lateral skull margin with other members of the genus, but differs from all others in that the skull is relatively narrower at its widest point and the orbits are larger, more elliptical, and placed more anteriorly. The snout is relatively broader and more robust, the choana shorter and more rounded, and the palatal tusks are proportionately larger than in other species. Premaxillary apertures, larger than those of E. woschmidti, penetrate the skull roof anterior to and separate from the external nares. E. appetolatus forms the sister taxon of the more gracile E. wellesi from Arizona, with which it shares the wide separation of postorbital and prefrontal. The size range of material from the locality is represented by skulls 227–472 mm in midline length. Preliminary allometric study indicates that the preorbital snout grows relatively longer and the orbits migrate posteriorly throughout ontogeny. The snout is relatively slender in young animals and grows wider and more robust throughout life. Application of beam mechanics shows mediolateral strengthening of the anterior teeth, which probably implies a preference for side-strike prey capture.