[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Allosaurus skin



Waylon Rowley wrote-

>      I was browsing
> www.westernpaleolabs.com/data/WesternInfo.doc when I
> noticed mention of a skin impression found during the
> preparation of a young _Allosaurus_. Is there any
> further info on this find?

>From JVP 23(3) 87A-88A.

A JUVENILE ALLOSAUR WITH PRESERVED INTEGUMENT FROM THE BASAL MORRISON
FORMATION OF CENTRAL WYOMING
PINEGAR, Richard Tyler, Provo, UT; LOEWEN, Mark A., Utah Museum of Natural
History, Salt Lake City, UT; CLOWARD, Karen C., HUNTER, Rick J. Western
Paleo Laboratories, Lehi, UT; and WEEGE, Christopher J., EnCana Oil and Gas
(USA) Inc., Denver, CO.

    Recent excavations at the Meilyn Quarry near Medicine Bow, Wyoming have
produced a large adult allosaur and a new specimen interpreted as a juvenile
of the same species. They were recovered 11 meters above the base of the
Morrison Formation within a fine-grained sandstone with depositional
features indicating an ephemeral fluvial system. Taphonomic indicators,
including a high degree of articulation and skin impressions, argue for
little to no fluvial transport and the presence of soft tissues at the time
of burial.
    Disarticulated cranial material includes both dentaries, surangulars,
prearticulars, splenials, hyoids, jugals, quadratojugals, quadrates,
squamosals and pterygoids, right articular, maxilla, palatine and vomer,
left postorbital and prefrontal, and a partial braincase. Most of the
vertebral column, ribs and gastralia are represented, except the atlas, axis
and some midcaudals. Limb materials include shoulder girdles, forelimbs and
the right hindlimb. The left side of the body preserves a 30 cm2 skin
impression consisting of small scales 2-3 mm in diameter. This suggests that
juvenile allosaurs possessed scaly integument. This represents the most
derived tetanuran to retain this character, otherwise present in more basal
theropods such as Carnotaurus.
    Overall length of the specimen is estimated at 4 m with a hip height of
1 m and skull length of 36 cm, suggesting that this animal is a juvenile.
Furthermore, size-independent morphological characteristics - including open
cranial and postcranial sutures, forelimb and hindlimb proportions, and
juvenile bone surface texture - are also indicative of a juvenile specimen.
    Comparisons with juvenile and adult allosaur material from the
Cleveland-Lloyd Quarry, and material of a new allosaur (DINO 11541), suggest
that this new specimen is not Allosaurus fragilis, based primarily on a
relatively flat ventral jugal margin, and the shape of the caudal neural
spines. These characters together with a wide obturator notch on the pubis
of the adult specimen are consistent with characters present on DINO 11541,
suggesting that these two animals belong to a distinct species of
Allosaurus.

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html