Re: Qijianglong, new mamenchisaurid sauropod from Late Jurassic of China (free pdf)

[Tim Williams <tijawi@gmail.com>]

As the authors make clear, with a great deal of restraint, the
taxonomy of Mamenchisauridae is an unholy mess - and a review is
apparently in the pipeline.  At my count, there are six species of
_Mamenchisaurus_ and seven species of _Omeisaurus_ - although this is
assuming _Zigongosaurus_ is a distinct genus.  Plus, there are other
mamenchisaurids (or putative mamenchisaurids), each of which is
monotypic: _Tonganosaurus_, _Eomamenchisaurus_, _Yuanmousaurus_,
_Chuanjiesaurus_, _Hudiesaurus_, _Tienshanosaurus_, _Xinjiangtitan_,
_Huangshanlong_, and now _Qijianglong_.  So at first glance, this was
quite a diverse and speciose group.

Any future review will likely split up _Mamenchisaurus_ and
_Omeisaurus_, likely spinning off new genera in the process.  But this
would be partly offset if other mamenchisaurid genera are sunk as
junior synonyms of other taxa. Some might not be mamenchisaurids at
all - such as _Omeisaurus_, which some phylogenetic analyses have put
outside Mamenchisauridae.  (Xing et al.'s phylogenetic definition of
Mamenchisaurus is unhelpful, in assuming that _Mamenchisaurus_ and
_Omeisaurus_ form a clade to the excluson of _Cetiosaurus_,
_Shunosaurus_, etc).

In any case, Xing et al. find the Mamenchisauridae to be quite basal
within sauropods, with a position at the very base of Eusauropoda.
Mamenchisaurids might have been the first really successful radiation
of sauropods (although their geographic range was limited to Asia, as
far as we know).  If true, they were the first sauropods to evolve
super-long necks, and did so rather early in sauropod evolution.




Cheers
Tim



On Sun, Feb 8, 2015 at 7:09 PM, Ben Creisler <bcreisler@gmail.com> wrote:
> Note that the pdf is now free:
>
>
> http://www.tandfonline.com/doi/pdf/10.1080/02724634.2014.889701
>
> On Tue, Jan 27, 2015 at 7:50 AM, Ben Creisler <bcreisler@gmail.com> wrote:
>> Ben Creisler
>> bcreisler@gmail.com
>>
>> A new online paper:
>>
>> Lida Xing, Tetsuto Miyashita, Jianping Zhang, Daqing Li, Yong Ye, Toru
>> Sekiya, Fengping Wang & Philip J. Currie (2015)
>> A new sauropod dinosaur from the Late Jurassic of China and the
>> diversity, distribution, and relationships of mamenchisaurids.
>> Journal of Vertebrate Paleontology (advance online publication)
>> DOI:10.1080/02724634.2014.889701
>> http://www.tandfonline.com/doi/full/10.1080/02724634.2014.889701#.VMexhWjF_To
>>
>> Qijianglong guokr, gen. et sp. nov., represents a mamenchisaurid
>> eusauropod from the Late Jurassic of southern China. The holotype
>> consists of an incomplete skull, partly articulated axial skeleton,
>> and fragmentary appendicular skeleton. A well-preserved braincase and
>> skull roof provide rare insights into the poorly known neurocranial
>> anatomy of mamenchisaurids and reveal a unique combination of
>> characters such as an accessory tuber at the base of planar
>> basipterygoid process and parietal excluding frontal from the anterior
>> margin of the supratemporal fenestra. The cervical vertebrae have a
>> distinct finger-like process extending from the postzygapophyseal
>> process beside a zygapophyseal contact. Qijianglong is the first
>> mamenchisaurid from the Late Jurassic of China that is definitively
>> distinct from Mamenchisaurus, indicating greater morphological and
>> taxonomic diversity of the poorly represented Late Jurassic
>> mamenchisaurids. The occurrence of Qijianglong is consistent with a
>> scenario in which mamenchisaurids formed an endemic sauropod fauna in
>> the Late Jurassic of Asia. Phylogenetically, Qijianglong represents a
>> relatively plesiomorphic mamenchisaurid lineage. The mamenchisaurids
>> form an ancient clade of basal eusauropod dinosaurs that likely
>> appeared in the Early Jurassic. A cladistic analysis highlights the
>> interrelationships of mamenchisaurids and suggests guidelines for
>> mamenchisaurid taxonomic revision. It may be desirable to restrict
>> generic names to the type species in order to avoid confusion.
>>
>> http://zoobank.org/urn:lsid:zoobank.org:pub:F93276CF-71FE-472E-9114-68294547C2A9
>>
>> SUPPLEMENTAL DATA—Supplemental materials are available for this
>> article for free at www.tandfonline.com/UJVP