[dinosaur] Embolomerous tetrapods from Nova Scotia + Permian tetrapod dentition

Ben Creisler
[email protected]

New papers:

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Gabrielle Ruth Adams, Arjan Mann Mann & Hillary C. Maddin (2019)
New embolomerous tetrapod material and a faunal overview of the
Mississippian-aged Point Edward Locality, Nova Scotia, Canada.
Canadian Journal of Earth Sciences (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1139_cjes-2D2018-2D0326&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=bFBNhea0Xva3UiHHd3ofLed0YOUoIus4kx-62OYIQhw&s=36ovBjGTYZojqaQiyVghp_uCa8bad5eiLGqKX9dRq_I&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.nrcresearchpress.com_doi_abs_10.1139_cjes-2D2018-2D0326-23.XXkTRS5KjX4&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=bFBNhea0Xva3UiHHd3ofLed0YOUoIus4kx-62OYIQhw&s=aIEMGI9xkQPNeFrb43gZXFcPNOfJlTkCxBKKIqnYXk0&e= 


Embolomerous tetrapods, mid-to-large aquatic predators, form a major faunal
constituent of Permo-Carboniferous tetrapod communities. Embolomeres are
recognized by their distinct circular, bipartite vertebrae. Although
traditionally classified as stem amniotes, the inclusion of embolomeres
within the tetrapod crown group has recently been challenged. Despite the
group’s phylogenetic uncertainty, embolomeres provide an important record
of a long-lived tetrapod lineage, spanning 'Romer’s Gap' through to the
Early Permian. Here we describe embolomerous tetrapod material that was
collected in 1915 by W. A. Bell (CMN 10015, herein divided into CMN 10015A,
B and C). The material, comprised of numerous disarticulated cranial and
postcranial elements, was discovered near Sydney, Nova Scotia, as ex situ
beach-float pertaining to a horizon within the Mississippian-aged Point
Edward Formation. Of this material, a single left lower jaw of a
proterogyrinid is identified, differing from previous embolomere remains
from this site identified as ?Pholiderpeton bretonense. We also identify an
anterior jaw fragment as a separate taxon from the proterogyrinid,
indicating the presence of at least two embolomerous tetrapods in Bell’s
collection. Other cranial and postcranial material cannot be directly
associated with either jaw and are not diagnostic enough to assign to a
specific taxon. Thus, the remaining material is referred to 'Embolomeri
indet. until more information is available. Additionally, we summarize the
fauna of the Point Edward locality revealing a diverse aquatic Upper
Mississippian ecosystem. Finally, the extensive embolomere material
described here presents new data that can broadly address embolomere
diversity throughout the Carboniferous.

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Yara Haridy, Bryan M. Gee, Florian Witzmann, Joseph J. Bevitt and Robert R.
Reisz (2019)
Retention of fish-like odontode overgrowth in Permian tetrapod dentition
supports outside-in theory of tooth origins.
Biology Letters 15(9): 20190514
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1098_rsbl.2019.0514&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=bFBNhea0Xva3UiHHd3ofLed0YOUoIus4kx-62OYIQhw&s=gkA5S3KCniTHx9AVdJ6sTNmoD4PqpKrNX8_7Hdp0z9k&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_doi_10.1098_rsbl.2019.0514&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=bFBNhea0Xva3UiHHd3ofLed0YOUoIus4kx-62OYIQhw&s=pSkI2OpSZQEyV2BV5qThnaUBaswweR_X5mFX6uyyGps&e= 

Free supplement:

https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_action_downloadSupplement-3Fdoi-3D10.1098-252Frsbl.2019.0514-26file-3Drsbl20190514supp1.pdf&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=bFBNhea0Xva3UiHHd3ofLed0YOUoIus4kx-62OYIQhw&s=VpYi6QVw6703WTm1YcsFDxlQlYCD_yStgvdlulHi_do&e= 


Teeth are often thought of as structures that line the margins of the
mouth; however, tooth-like structures called odontodes are commonly found
on the dermal bones of many Palaeozoic vertebrates including early jawless
fishes. 'Odontode' is a generalized term for all tooth-like dentine
structures that have homologous tissues and development. This definition
includes true teeth and the odontodes of early 'fishes', which have been
recently examined to gain new insights into the still unresolved origin of
teeth. Two leading hypotheses are frequently referenced in this debate: the
'utside-in hypothesis, which posits that dermal odontodes evolutionarily
migrate into the oral cavity, and the 'inside-out' hypothesis, which posits
that teeth originated in the oropharyngeal cavity and then moved outwards
into the oral cavity. Here, we show that, unlike the well-known one-to-one
replacement patterns of marginal dentition, the palatal dentition of the
early Permian tetrapods, including the dissorophoid amphibian Cacops and
the early reptile Captorhinus, is overgrown by a new layer of bone to which
the newest teeth are then attached. This same overgrowth pattern has been
well documented in dermal and oral odontodes (i.e. teeth) of early fishes.
We propose that this pattern represents the primitive condition for
vertebrates and may even predate the origin of jaws. Therefore, this
pattern crosses the fish–tetrapod transition, and the retention of this
ancestral pattern in the palatal dentition of early terrestrial tetrapods
provides strong support for the 'outside-in' hypothesis of tooth origins.

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