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Re: Ankylosuchus, new doswelliid archosauromorph from Upper Triassic of Texas (free pdf)



The holotype specimen is actually from the Dockum Group; however,
these authors have proposed subsuming the Dockum under the Chinle
Formation (historically not identified in Texas) by raising the Chinle
to Group status. First proposed in the early 1990s his has been
controversial and not used by many workers other than Spencer Lucas
and his colleagues. The new name appears to be an attempt to reinforce
the issue, but is unfortunate because it is confusing.

A recent paper by a group of mappers in New Mexico seeks to clarify
these nomenclatural issues.  They propose retaining Dockum for Texas
and eastern New Mexico, and keeping the Chinle as at the formational
rank in Utah, Arizona, and western New Mexico.

http://chinleana.fieldofscience.com/2013/12/standardizing-triassic-stratigraphic.html

On Mon, Dec 23, 2013 at 4:34 AM, Jaime Headden <qi_leong@hotmail.com> wrote:
> Note: "chinlegroupensis," not "chinlensis" as has been popular previously. 
> Pushing the limits here.
>
> Cheers,
>
>   Jaime A. Headden
>   The Bite Stuff (site v2)
>   http://qilong.wordpress.com/
>
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
>
> "Ever since man first left his cave and met a stranger with a
> different language and a new way of looking at things, the human race
> has had a dream: to kill him, so we don't have to learn his language or
> his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
> Backs)
>
>
> ----------------------------------------
>> Date: Mon, 23 Dec 2013 00:03:36 -0800
>> From: bcreisler@gmail.com
>> To: dinosaur@usc.edu
>> Subject: Ankylosuchus, new doswelliid archosauromorph from Upper Triassic of 
>> Texas (free pdf)
>>
>> From: Ben Creisler
>> bcreisler@gmail.com
>>
>> A new recent paper not yet mentioned. The pdf is free at the link:
>>
>> Spencer G. Lucas, Justin A. Spielmann and Adrian P. Hunt (2013)
>> A new doswelliid archosauromorph from the Upper Triassic of West Texas.
>> in Tanner, L.H., Spielmann, J.A. and Lucas, S.G., eds., 2013, The
>> Triassic System.
>> New Mexico Museum of Natural History and Science, Bulletin 61 : 382-388
>> Free pdf:
>> http://paleo.cortland.edu/globaltriassic2/Bulletin%2061%20Final/31-Lucas%20et%20al%20(Ankylosuchus).pdf
>>
>> Ankylosuchus chinlegroupensis is a new genus and species of
>> heavily-armored archosauromorph from the Otischalkian Colorado City
>> Formation of the Chinle Group in Howard County, West Texas. The
>> incomplete holotype skeleton consists of cranial and pelvic (?)
>> elements, vertebral centra, a partial limb shaft and numerous
>> osteoderms. The skull elements reveal a thick, heavily armored
>> braincase and skull roof with parasagittal crests. The relatively
>> short sacral vertebrae suggest an animal less than 1 meter in total
>> body length, not including the tail. The morphology of the osteoderms
>> does not match any currently known armored archosauromorph, but it is
>> most similar to doswelliids. Most of the osteoderms posse
>> closely packed pits that form no obvious pattern. Some osteoderms have
>> raised, linear ridges running across them and others have anterior
>> laminae with faint patterning on the articular surface. Some of the
>> osteoderms are tightly sutured to each other via digitate sutures; all
>> are relatively thick. The patterning of the ostoderms matches well
>> with that of doswellids in being coarse, deeply incised and mostly
>> composed of equal-sized pits and in the possession of anterior
>> laminae. Even so, these osteoderms are readily distinguished from
>> those of Doswellia, the only doswelliid previously reported from the
>> Chinle Group, by their coarser pitting, greater thickness and (at
>> least in some osteoderms) fusion with laterally adjacent osteoderms
>> along their mutual sutural boundaries. A. chinlegroupensis is derived
>> from the oldest strata of the Texas Chinle Group, the Otischalkian,
>> whereas the genus Doswellia is known from the Chinle Group in Texas,
>> New Mexico and Utah, in strata of Otischalkian-Adamanian (late
>> Carnian) age. Doswelliids are very rare, but visible components of
>> global Triassic faunas. They include Tarjadia (= Archeopelta) from the
>> Berdyankian (Ladinian) of Argentina and Brazil, Doswellia from the
>> Otischalkian-Adamanian of the American Southwest and the Otischalkian
>> of the Newark Supergroup in the eastern USA, and now Ankylosuchus from
>> the Otischalkian of West Texas.