January 27, 2010

The Paleobiology of Coelophysis Part II: Other Critters in the Quarry

6:43 am

or, Token Diversity in a Dinosaur Graveyard

Although fossils of the Triassic theropod Coelophysis bauri are by far the most numerous vertebrate remains preserved in blocks from the Whitaker quarry, several other animals are known from the site as well. Many have just been uncovered or described within the past ten years, and in the course of preparing the NMMNH block (and examining other blocks for comparison), several new fossils have come to light. A brief, annotated list of other fauna known from the quarry appears below:

Invertebrates: As mentioned last time, ostracods (Darwinula sp.) and conchostracans (Shipingia) were found in a sandy layer below the bones, remnants of temporary ponding at the site prior to the Coelophysis burial.


Synorichthys chased by Chinlea, sculpted by Gary Staab

Fish: Schaeffer (1967) reported paleonisciform and coelacanth fish in association with Coelophysis at Ghost Ranch. Both were found in the NMMNH block above the invertebrate layer and just below the lowest tetrapod bones: scaly little redfieldiid paleonisciforms, tentatively assigned to Synorichthys, and bits of fin, scale, and skull from the large coelacanth Chinlea sorenseni. As these fish would have been too large to thrive in the type of ephemeral pond indicated by the invertebrates, we posited that floodwaters washed them in to the site from a larger body of water.

Whitakersaurus bermani: This diminutive sphenodontian (my tiny-tuatara-based restoration at the left) is known from pieces of the upper and lower jaw found within 2 centimeters of the edge of the NMMNH block. The largest piece of the holotype, an incomplete right dentary preserving nineteen tooth-positions, is about 5 millimeters long (Heckert et al. 2008).

Drepanosaurs: Harris & Downs (2002) reported the first drepanosaur material from the quarry—a well-preserved (but isolated) shoulder girdle from the block at the Ruth Hall Museum of Paleontology. In a new review of the drepanosaurs, Renesto et al. (2010) assign that shoulder girdle to the genus Drepanosaurus, and describe a partially articulated but generically indeterminate foot on the edge of the NMMNH block (pictured below).


NMMNH P-57651, the foot of a small drepanosaur, preserved portion roughly 5cm long

Vancleavea campi: By far the most complete specimens of this armor-coated reptile are two beautifully articulated skeletons from the Ruth Hall Museum block, recently described by Nesbitt et al. (2009). Remains of a partial, disarticulated skeleton are associated with some characteristic Vancleavea armor in a mostly unprepared fossil removed from the NMMNH block.


Vancleavea sculpture by Phil Bircheff at the Ruth Hall Museum of Paleontology.

Phytosaurs: An ~80cm long phytosaur skull from the Whitaker/Coelophysis quarry (the holotype of Redondasaurus bermani Hunt and Lucas 1993) is housed at the Carnegie Museum. The skull and lower jaws of a juvenile phytosaur were found in the NMMNH block, currently exposed in left lateral/palatal view on a partially prepared jacket removed from the main block (photo below).


NMMNH P-44920, juvenile phytosaur (Redondasaurus?) skull and jaws, left lateral/palatal view. Photo courtesy of Larry Rinehart.

Postosuchus kirkpatricki: The Carnegie Museum of Natural History and the Ruth Hall Museum of Paleontology both have specimens of this rauisuchian on Whitaker/Coelophysis quarry blocks. These were partially figured in Long and Murry (1995, figs 145–146).


Effigia sculpture by Phil Bircheff
at the Ruth Hall Museum of Paleontology.

Effigia okeefeae: The type specimens of this bipedal suchian were recently discovered in jackets pulled from the quarry during the early excavations by the American Museum (Nesbitt & Norell 2006, Nesbitt 2007). A scapula and coracoid found in the NMMNH block might belong to this animal.

Hesperosuchus agilis: One of the best-preserved specimens of this early crocodylomorph is an articulated skull and partial skeleton now at the Carnegie Museum (Clark et al. 2000). Only a few armor scutes are known from the NMMNH block.

To the best of my knowledge, this little bestiary lists pretty much all the non-Coelophysis animals identified from Ghost Ranch Whitaker quarry fossils. All of them, that is, with one interesting exception, noticed while reviewing specimens on other Coelophysis blocks. Its story will make up the bulk of the next post.

Next time: Truly, Coelophysis?
or, The Mysterious Canadian

Previously:
Introduction

 

—Matt Celeskey.

File under: Bony Fish, Dinosaurs, Recent Discoveries, Reptiles, Triassic.

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