[dinosaur] Champsosaurus skull CT analysis + lizard iliosacral joint

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Ben [email protected]=0A=0ASome recent non-dino papers:=0A=0A=
=3D=3D=3D=3D=3D=3D=3D=3D=0A=0AFree pdf:=0A=0AThomas W. Dudgeon, Hillary C. =
Maddin, David C. Evans & Jordan C. Mallon=0A(2020)=0AComputed tomography an=
alysis of the cranium of Champsosaurus lindoei and=0Aimplications for chori=
stoderan neomorphic ossification.=0AJournal of Anatomy (advance online publ=
ication)=0Adoi:  https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__doi=
.org_10.1111_joa.13134&d=3DDwIFaQ&c=3DclK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CS=
fnc_gI&r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3DkYDhf4hakt6IqMq-=
zIsdcO2C4zDpGYIkL5jjR2WYJBc&s=3DNNoGAXDfswV-Ml-3dgyijcKPiq2JdQg8r7r3vWDSJNw=
&e=3D=20=0Ahttps://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__onlinelib=
rary.wiley.com_doi_10.1111_joa.13134&d=3DDwIFaQ&c=3DclK7kQUTWtAVEOVIgvi0NU5=
BOUHhpN0H8p7CSfnc_gI&r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3DkY=
Dhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&s=3D5iW4tRt8pe3th2bLS39_-cVQ0mgeb=
tx_sGxFjfxq9Dw&e=3D=20=0A=0AFree pdf:=0Ahttps://urldefense.proofpoint.com/v=
2/url?u=3Dhttps-3A__onlinelibrary.wiley.com_doi_pdf_10.1111_joa.13134&d=3DD=
wIFaQ&c=3DclK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=3DRy_mO4IFaUmGof_Yl=
9MyZgecRCKHn5g4z1CYJgFW9SI&m=3DkYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&=
s=3D0QI3-t0pSJvZTntCyVt65P7R2DR2Q3zFGH7br758wnY&e=3D=20=0A=0A=0A=0AChoristo=
deres are extinct neodiapsid reptiles that are well known for their=0Aunusu=
al cranial anatomy, possessing an elongated snout and expanded=0Atemporal a=
rches. Although choristodere skulls are well described=0Aexternally, their =
internal anatomy remains unknown. An internal description=0Awas needed to s=
hed light on peculiarities of the choristodere skull, such=0Aas paired gaps=
 on the ventral surface of the skull that may pertain to the=0Afenestra ova=
lis, and a putative neomorphic ossification in the lateral wall=0Aof the br=
aincase. Our goals were: (i) to describe the cranial elements of=0AChampsos=
aurus lindoei in three dimensions; (ii) to describe paired gaps on=0Athe ve=
ntral surface of the skull to determine if these are indeed the=0Afenestrae=
 ovales; (iii) to illustrate the morphology of the putative=0Aneomorphic bo=
ne; and (iv) to consider the possible developmental and=0Afunctional origin=
s of the neomorph. We examined the cranial anatomy of the=0Achoristodere Ch=
ampsosaurus lindoei (CMN 8920) using high=E2=80=90resolution=0Amicro=E2=80=
=90computed tomography scanning. We found that the paired gaps on the=0Aven=
tral surface of the skull do pertain to the fenestrae ovales, an unusual=0A=
arrangement that may be convergent with some plesiosaurs, some aistopods,=
=0Aand some urodeles. The implications of this morphology in Champsosaurus =
are=0Aunknown and will be the subject of future work. We found that the=0An=
eomorphic bone is a distinct ossification, but is not part of the wall of=
=0Athe brain cavity or the auditory capsule. Variation in the developmental=
=0Apathways of cranial bones in living amniotes was surveyed to determine h=
ow=0Athe neomorphic bone may have developed. We found that the chondrocrani=
um=0Aand splanchnocranium show little to no variation across amniotes, and =
the=0Aneomorphic bone is therefore most likely to have developed from the=
=0Adermatocranium; however, the stapes is a pre=E2=80=90existing cranial el=
ement that=0Ais undescribed in choristoderes and may be homologous with the=
 neomorphic=0Abone. If the neomorphic bone is not homologous with the stape=
s, the=0Aneomorph likely developed from the dermatocranium through incomple=
te fusion=0Aof ossification centres from a pre=E2=80=90existing bone, most =
likely the parietal.=0ABased on the apparent morphology of the neomorph in =
Coeruleodraco, the=0Aneomorph was probably too small to play a significant =
structural role in=0Athe skull of early choristoderes and it may have arise=
n through=0Anon=E2=80=90adaptive means. In neochoristoderes, such as Champs=
osaurus, the=0Aneomorph was likely recruited to support the expanded tempor=
al arches.=0A=0A=3D=3D=3D=3D=0A=0AIlaria Paparella, Aaron R. H. LeBlanc, Mi=
chael R. Doschak & Michael W.=0ACaldwell (2020)=0AThe iliosacral joint in l=
izards: an osteological and histological analysis.=0AJournal of Anatomy (ad=
vance online publication)=0Adoi:  https://urldefense.proofpoint.com/v2/url?=
u=3Dhttps-3A__doi.org_10.1111_joa.13132&d=3DDwIFaQ&c=3DclK7kQUTWtAVEOVIgvi0=
NU5BOUHhpN0H8p7CSfnc_gI&r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=
=3DkYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&s=3DKr5YuYXGwT0W-aa5L8UVbI37=
u1C2eO__IMbgEvT0ck8&e=3D=20=0Ahttps://urldefense.proofpoint.com/v2/url?u=3D=
https-3A__onlinelibrary.wiley.com_doi_10.1111_joa.13132&d=3DDwIFaQ&c=3DclK7=
kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g=
4z1CYJgFW9SI&m=3DkYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&s=3D0dPtPpKhQ7=
mQy5GoR2OSod8Ne14H2oqwtDzQwdW52Uw&e=3D=20=0A=0A=0AThe development of the il=
iosacral joint (ISJ) in tetrapods represented a=0Acrucial step in the evolu=
tion of terrestrial locomotion. This structure is=0Aresponsible for transfe=
rring forces between the vertebral column and=0Aappendicular skeleton, thus=
 supporting the bodyweight on land. However,=0Amost research dealing with t=
he water=E2=80=90to=E2=80=90land transition and biomechanical=0Astudies in =
general has focused exclusively on the articulation between the=0Apelvic gi=
rdle and femur. Our knowledge about the contact between the pelvic=0Agirdle=
 and vertebral column (i.e. the ISJ) at a tissue level is restricted=0Aso f=
ar to human anatomy, with little to no information available on other=0Atet=
rapods. This lack of data limits our understanding of the development=0Aand=
 evolution of such a key structure, and thus on the pattern and=0Aprocesses=
 of the evolution of terrestrial locomotion. Therefore, we=0Ainvestigated t=
he macro=E2=80=90 and microanatomy of the ISJ in limb=E2=80=90bearing=0Asqu=
amates that, similar to most non=E2=80=90mammalian, non=E2=80=90avian tetra=
pods, possess=0Aonly two sacral ribs articulating with the posterior proces=
s of the ilium.=0AUsing a combination of osteology, micro=E2=80=90computed =
tomography and histology,=0Awe collected data on the ISJ apparatus of numer=
ous specimens, sampling=0Adifferent taxa and different ontogenetic stages. =
Osteologically, we=0Arecorded consistent variability in all three processes=
 of the ilium=0A(preacetabular, supracetabular and posterior) and sacral ri=
bs that=0Acorrelate with posture and locomotion. The presence of a cavity b=
etween the=0Ailium and sacral ribs, abundant articular cartilage and fibroc=
artilage, and=0Aa surrounding membrane of dense fibrous connective tissue a=
llowed us to=0Adefine this contact as a synovial joint. By comparison, the =
two sacral ribs=0Aare connected to each other mostly by dense fibrous tissu=
e, with some=0Acartilage found more distally along the margins of the two r=
ibs, defining=0Athis joint as a combination of a syndesmosis and synchondro=
sis. Considering=0Athe intermediary position of the ISJ between the axial a=
nd appendicular=0Askeletons, the shape of the articular surfaces of the sac=
ral ribs and=0Ailium, and the characteristics of the muscles associated wit=
h this=0Astructure, we argue that the mobility of the ISJ is primarily driv=
en by the=0Amovements of the hindlimb during locomotion. We hypothesize tha=
t limited=0Atorsion of the ilium at the ISJ happens when the hip is abducte=
d, and the=0Ajoint is likely able to absorb the compressional and extension=
al forces=0Arelated to the protraction and retraction of the femur. The mix=
 of fibres=0Aand cartilage between the two sacral ribs instead serves prima=
rily as a=0Ashock absorber, with the potential for limited vertical transla=
tion during=0Alocomotion.=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>Some recent n=
on-dino papers:<br><div><br></div><div>=3D=3D=3D=3D=3D=3D=3D=3D</div><div><=
br></div><div>Free pdf:</div><div><br>Thomas W. Dudgeon, Hillary C. Maddin,=
 David C. Evans &amp; Jordan C. Mallon (2020)<br>Computed tomography analys=
is of the cranium of Champsosaurus lindoei and implications for choristoder=
an neomorphic ossification.<br>Journal of Anatomy (advance online publicati=
on)<br>doi: =C2=A0<a href=3D"https://urldefense.proofpoint.com/v2/url?u=3Dh=
ttps-3A__doi.org_10.1111_joa.13134&amp;d=3DDwMFaQ&amp;c=3DclK7kQUTWtAVEOVIg=
vi0NU5BOUHhpN0H8p7CSfnc_gI&amp;r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW=
9SI&amp;m=3DkYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&amp;s=3DNNoGAXDfswV=
-Ml-3dgyijcKPiq2JdQg8r7r3vWDSJNw&amp;e=3D">https://doi.org/10.1111/joa.1313=
4</a><br><a href=3D"https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__=
onlinelibrary.wiley.com_doi_10.1111_joa.13134&amp;d=3DDwMFaQ&amp;c=3DclK7kQ=
UTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&amp;r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn=
5g4z1CYJgFW9SI&amp;m=3DkYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&amp;s=3D=
5iW4tRt8pe3th2bLS39_-cVQ0mgebtx_sGxFjfxq9Dw&amp;e=3D">https://onlinelibrary=
.wiley.com/doi/10.1111/joa.13134</a></div><div><br>Free pdf:<br><a href=3D"=
https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__onlinelibrary.wiley.=
com_doi_pdf_10.1111_joa.13134&amp;d=3DDwMFaQ&amp;c=3DclK7kQUTWtAVEOVIgvi0NU=
5BOUHhpN0H8p7CSfnc_gI&amp;r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&a=
mp;m=3DkYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&amp;s=3D0QI3-t0pSJvZTntC=
yVt65P7R2DR2Q3zFGH7br758wnY&amp;e=3D">https://onlinelibrary.wiley.com/doi/p=
df/10.1111/joa.13134</a></div><div><br></div><div><br><br>Choristoderes are=
 extinct neodiapsid reptiles that are well known for their unusual cranial =
anatomy, possessing an elongated snout and expanded temporal arches. Althou=
gh choristodere skulls are well described externally, their internal anatom=
y remains unknown. An internal description was needed to shed light on pecu=
liarities of the choristodere skull, such as paired gaps on the ventral sur=
face of the skull that may pertain to the fenestra ovalis, and a putative n=
eomorphic ossification in the lateral wall of the braincase. Our goals were=
: (i) to describe the cranial elements of Champsosaurus lindoei in three di=
mensions; (ii) to describe paired gaps on the ventral surface of the skull =
to determine if these are indeed the fenestrae ovales; (iii) to illustrate =
the morphology of the putative neomorphic bone; and (iv) to consider the po=
ssible developmental and functional origins of the neomorph. We examined th=
e cranial anatomy of the choristodere Champsosaurus lindoei (CMN 8920) usin=
g high=E2=80=90resolution micro=E2=80=90computed tomography scanning. We fo=
und that the paired gaps on the ventral surface of the skull do pertain to =
the fenestrae ovales, an unusual arrangement that may be convergent with so=
me plesiosaurs, some aistopods, and some urodeles. The implications of this=
 morphology in Champsosaurus are unknown and will be the subject of future =
work. We found that the neomorphic bone is a distinct ossification, but is =
not part of the wall of the brain cavity or the auditory capsule. Variation=
 in the developmental pathways of cranial bones in living amniotes was surv=
eyed to determine how the neomorphic bone may have developed. We found that=
 the chondrocranium and splanchnocranium show little to no variation across=
 amniotes, and the neomorphic bone is therefore most likely to have develop=
ed from the dermatocranium; however, the stapes is a pre=E2=80=90existing c=
ranial element that is undescribed in choristoderes and may be homologous w=
ith the neomorphic bone. If the neomorphic bone is not homologous with the =
stapes, the neomorph likely developed from the dermatocranium through incom=
plete fusion of ossification centres from a pre=E2=80=90existing bone, most=
 likely the parietal. Based on the apparent morphology of the neomorph in C=
oeruleodraco, the neomorph was probably too small to play a significant str=
uctural role in the skull of early choristoderes and it may have arisen thr=
ough non=E2=80=90adaptive means. In neochoristoderes, such as Champsosaurus=
, the neomorph was likely recruited to support the expanded temporal arches=
.<br></div><div><br></div><div>=3D=3D=3D=3D</div><div><br></div><div>Ilaria=
 Paparella, Aaron R. H. LeBlanc, Michael R. Doschak &amp; Michael W. Caldwe=
ll (2020)<br>The iliosacral joint in lizards: an osteological and histologi=
cal analysis.<br>Journal of Anatomy (advance online publication)<br>doi: =
=C2=A0<a href=3D"https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__doi=
.org_10.1111_joa.13132&amp;d=3DDwMFaQ&amp;c=3DclK7kQUTWtAVEOVIgvi0NU5BOUHhp=
N0H8p7CSfnc_gI&amp;r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&amp;m=3D=
kYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&amp;s=3DKr5YuYXGwT0W-aa5L8UVbI3=
7u1C2eO__IMbgEvT0ck8&amp;e=3D">https://doi.org/10.1111/joa.13132</a><br><a =
href=3D"https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__onlinelibrar=
y.wiley.com_doi_10.1111_joa.13132&amp;d=3DDwMFaQ&amp;c=3DclK7kQUTWtAVEOVIgv=
i0NU5BOUHhpN0H8p7CSfnc_gI&amp;r=3DRy_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9=
SI&amp;m=3DkYDhf4hakt6IqMq-zIsdcO2C4zDpGYIkL5jjR2WYJBc&amp;s=3D0dPtPpKhQ7mQ=
y5GoR2OSod8Ne14H2oqwtDzQwdW52Uw&amp;e=3D">https://onlinelibrary.wiley.com/d=
oi/10.1111/joa.13132</a></div><div><br><br>The development of the iliosacra=
l joint (ISJ) in tetrapods represented a crucial step in the evolution of t=
errestrial locomotion. This structure is responsible for transferring force=
s between the vertebral column and appendicular skeleton, thus supporting t=
he bodyweight on land. However, most research dealing with the water=E2=80=
=90to=E2=80=90land transition and biomechanical studies in general has focu=
sed exclusively on the articulation between the pelvic girdle and femur. Ou=
r knowledge about the contact between the pelvic girdle and vertebral colum=
n (i.e. the ISJ) at a tissue level is restricted so far to human anatomy, w=
ith little to no information available on other tetrapods. This lack of dat=
a limits our understanding of the development and evolution of such a key s=
tructure, and thus on the pattern and processes of the evolution of terrest=
rial locomotion. Therefore, we investigated the macro=E2=80=90 and microana=
tomy of the ISJ in limb=E2=80=90bearing squamates that, similar to most non=
=E2=80=90mammalian, non=E2=80=90avian tetrapods, possess only two sacral ri=
bs articulating with the posterior process of the ilium. Using a combinatio=
n of osteology, micro=E2=80=90computed tomography and histology, we collect=
ed data on the ISJ apparatus of numerous specimens, sampling different taxa=
 and different ontogenetic stages. Osteologically, we recorded consistent v=
ariability in all three processes of the ilium (preacetabular, supracetabul=
ar and posterior) and sacral ribs that correlate with posture and locomotio=
n. The presence of a cavity between the ilium and sacral ribs, abundant art=
icular cartilage and fibrocartilage, and a surrounding membrane of dense fi=
brous connective tissue allowed us to define this contact as a synovial joi=
nt. By comparison, the two sacral ribs are connected to each other mostly b=
y dense fibrous tissue, with some cartilage found more distally along the m=
argins of the two ribs, defining this joint as a combination of a syndesmos=
is and synchondrosis. Considering the intermediary position of the ISJ betw=
een the axial and appendicular skeletons, the shape of the articular surfac=
es of the sacral ribs and ilium, and the characteristics of the muscles ass=
ociated with this structure, we argue that the mobility of the ISJ is prima=
rily driven by the movements of the hindlimb during locomotion. We hypothes=
ize that limited torsion of the ilium at the ISJ happens when the hip is ab=
ducted, and the joint is likely able to absorb the compressional and extens=
ional forces related to the protraction and retraction of the femur. The mi=
x of fibres and cartilage between the two sacral ribs instead serves primar=
ily as a shock absorber, with the potential for limited vertical translatio=
n during locomotion.<br></div></div></div>=0A=

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