[dinosaur] Tetrapod skull-neck boundary evolution (free pdf)

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Ben [email protected]=0A=0AA new paper with free pdf:=0A=0A=0A=
Hillary C. Maddin,  Nadine Piekarski,  Robert R. Reisz &  James Hanken=0A(2=
020)=0ADevelopment and evolution of the tetrapod skull-neck boundary.=0ABio=
logical Reviews (advance online publication)=0Adoi: https://urldefense.proo=
fpoint.com/v2/url?u=3Dhttps-3A__doi.org_10.1111_brv.12578&d=3DDwIFaQ&c=3Dcl=
K7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn=
5g4z1CYJgFW9SI&m=3DgLYBhzZMJyPzBS4TkY9x0cPBsx5bmuK2Z_V2glBKUmQ&s=3DKYCxmu2L=
cCCbmbCmHlA1cKcOGG2Nd2cB19tSGUwCnj8&e=3D=20=0Ahttps://urldefense.proofpoint=
.com/v2/url?u=3Dhttps-3A__onlinelibrary.wiley.com_doi_10.1111_brv.12578&d=
=3DDwIFaQ&c=3DclK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=3DRy_mO4IFaUmGo=
f_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3DgLYBhzZMJyPzBS4TkY9x0cPBsx5bmuK2Z_V2glBK=
UmQ&s=3DC4XjloGh6Yg-terau-Z2v7DOr4aMGr0LUzVPRTSMTrs&e=3D=20=0A=0AFree pdf:=
=0Ahttps://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__onlinelibrary.wil=
ey.com_doi_pdf_10.1111_brv.12578&d=3DDwIFaQ&c=3DclK7kQUTWtAVEOVIgvi0NU5BOUH=
hpN0H8p7CSfnc_gI&r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3DgLYBhz=
ZMJyPzBS4TkY9x0cPBsx5bmuK2Z_V2glBKUmQ&s=3DEgvxreufMi6ivbGrRUBtmb0rvMG3AS6D3=
4T_OZ_fSh0&e=3D=20=0A=0A=0AThe origin and evolution of the vertebrate skull=
 have been topics of=0Aintense study for more than two centuries. Whereas e=
arly theories of skull=0Aorigin, such as the influential vertebral theory, =
have been largely refuted=0Awith respect to the anterior (pre=E2=80=90otic)=
 region of the skull, the posterior=0A(post=E2=80=90otic) region is known t=
o be derived from the anteriormost paraxial=0Asegments, i.e. the somites. H=
ere we review the morphology and development=0Aof the occiput in both livin=
g and extinct tetrapods, taking into account=0Arevised knowledge of skull d=
evelopment by augmenting historical accounts=0Awith recent data. When occip=
ital composition is evaluated relative to its=0Aposition along the neural a=
xis, and specifically to the hypoglossal nerve=0Acomplex, much of the appar=
ent interspecific variation in the location of=0Athe skull=E2=80=93neck bou=
ndary stabilizes in a phylogenetically informative way.=0ABased on this cri=
terion, three distinct conditions are identified in (i)=0Afrogs, (ii) salam=
anders and caecilians, and (iii) amniotes. The position of=0Athe posteriorm=
ost occipital segment relative to the hypoglossal nerve is=0Akey to underst=
anding the evolution of the posterior limit of the skull. By=0Ausing crania=
l foramina as osteological proxies of the hypoglossal nerve, a=0Asurvey of =
fossil taxa reveals the amniote condition to be present at the=0Abase of Te=
trapoda. This result challenges traditional theories of cranial=0Aevolution=
, which posit translocation of the occiput to a more posterior=0Alocation i=
n amniotes relative to lissamphibians (frogs, salamanders,=0Acaecilians), a=
nd instead supports the largely overlooked hypothesis that=0Athe reduced oc=
ciput in lissamphibians is secondarily derived. Recent=0Aadvances in our un=
derstanding of the genetic basis of axial patterning and=0Aits regulation i=
n amniotes support the hypothesis that the lissamphibian=0Aoccipital form m=
ay have arisen as the product of a homeotic shift in=0Asegment fate from an=
 amniote=E2=80=90like condition.=0A=

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<div dir=3D"ltr"><div><br></div>Ben Creisler<div><a href=3D"mailto:bcreisle=
[email protected]">[email protected]</a></div><div><br></div><div>A new paper w=
ith free pdf:<br><div><br></div><div><br></div><div>Hillary C. Maddin, =C2=
=A0Nadine Piekarski, =C2=A0Robert R. Reisz &amp; =C2=A0James Hanken (2020)<=
br>Development and evolution of the tetrapod skull-neck boundary.<br>Biolog=
ical Reviews (advance online publication)<br>doi: <a href=3D"https://urldef=
ense.proofpoint.com/v2/url?u=3Dhttps-3A__doi.org_10.1111_brv.12578&amp;d=3D=
DwMFaQ&amp;c=3DclK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&amp;r=3DRy_mO4IF=
aUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&amp;m=3DgLYBhzZMJyPzBS4TkY9x0cPBsx5bmuK=
2Z_V2glBKUmQ&amp;s=3DKYCxmu2LcCCbmbCmHlA1cKcOGG2Nd2cB19tSGUwCnj8&amp;e=3D">=
https://doi.org/10.1111/brv.12578</a><br><a href=3D"https://urldefense.proo=
fpoint.com/v2/url?u=3Dhttps-3A__onlinelibrary.wiley.com_doi_10.1111_brv.125=
78&amp;d=3DDwMFaQ&amp;c=3DclK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&amp;r=
=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&amp;m=3DgLYBhzZMJyPzBS4TkY9x=
0cPBsx5bmuK2Z_V2glBKUmQ&amp;s=3DC4XjloGh6Yg-terau-Z2v7DOr4aMGr0LUzVPRTSMTrs=
&amp;e=3D">https://onlinelibrary.wiley.com/doi/10.1111/brv.12578</a><br><br=
>Free pdf:<br><a href=3D"https://urldefense.proofpoint.com/v2/url?u=3Dhttps=
-3A__onlinelibrary.wiley.com_doi_pdf_10.1111_brv.12578&amp;d=3DDwMFaQ&amp;c=
=3DclK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&amp;r=3DRy_mO4IFaUmGof_Yl9My=
ZgecRCKHn5g4z1CYJgFW9SI&amp;m=3DgLYBhzZMJyPzBS4TkY9x0cPBsx5bmuK2Z_V2glBKUmQ=
&amp;s=3DEgvxreufMi6ivbGrRUBtmb0rvMG3AS6D34T_OZ_fSh0&amp;e=3D">https://onli=
nelibrary.wiley.com/doi/pdf/10.1111/brv.12578</a><br><br><br></div><div>The=
 origin and evolution of the vertebrate skull have been topics of intense s=
tudy for more than two centuries. Whereas early theories of skull origin, s=
uch as the influential vertebral theory, have been largely refuted with res=
pect to the anterior (pre=E2=80=90otic) region of the skull, the posterior =
(post=E2=80=90otic) region is known to be derived from the anteriormost par=
axial segments, i.e. the somites. Here we review the morphology and develop=
ment of the occiput in both living and extinct tetrapods, taking into accou=
nt revised knowledge of skull development by augmenting historical accounts=
 with recent data. When occipital composition is evaluated relative to its =
position along the neural axis, and specifically to the hypoglossal nerve c=
omplex, much of the apparent interspecific variation in the location of the=
 skull=E2=80=93neck boundary stabilizes in a phylogenetically informative w=
ay. Based on this criterion, three distinct conditions are identified in (i=
) frogs, (ii) salamanders and caecilians, and (iii) amniotes. The position =
of the posteriormost occipital segment relative to the hypoglossal nerve is=
 key to understanding the evolution of the posterior limit of the skull. By=
 using cranial foramina as osteological proxies of the hypoglossal nerve, a=
 survey of fossil taxa reveals the amniote condition to be present at the b=
ase of Tetrapoda. This result challenges traditional theories of cranial ev=
olution, which posit translocation of the occiput to a more posterior locat=
ion in amniotes relative to lissamphibians (frogs, salamanders, caecilians)=
, and instead supports the largely overlooked hypothesis that the reduced o=
cciput in lissamphibians is secondarily derived. Recent advances in our und=
erstanding of the genetic basis of axial patterning and its regulation in a=
mniotes support the hypothesis that the lissamphibian occipital form may ha=
ve arisen as the product of a homeotic shift in segment fate from an amniot=
e=E2=80=90like condition.<br><br></div></div></div>=0A=

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