Planocraniidae

Prior to 2013, the term Pristichampsidae/Pristichampsinae was used for this group. However, the type specimen of Pristichampsus was found to be undiagnostic, and considered to be a nomen dubium. As such, Brochu (2013) transferred the other species placed in Pristichampsus to Boverisuchus, and resurrected Planocraniidae to replace Pristichampsidae/Pristichampsinae as the name for the clade. Brochu cladistically defined Planocraniidae as Planocrania hengdongensis and crocodyliforms more closely related to it than to Alligator mississippiensis (American alligator), Crocodylus niloticus (Nile crocodile), Gavialis gangeticus (gharial), Thoracosaurus macrorhynchus, Allodaposuchus precedens, or Hylaeochampsa vectiana.

Phylogenetic analyses based purely on morphological data have generally placed planocraniids in a basal position within the crocodilian crown group. Some of these analyses have found that planocraniids lie just outside Brevirostres, a group that includes alligators, caimans, and crocodiles but not gharials.{{Cite journal|author1=Adam P. Cossette |author2=Christopher A. Brochu |year=2020 |title=A systematic review of the giant alligatoroid Deinosuchus from the Campanian of North America and its implications for the relationships at the root of Crocodylia |journal=Journal of Vertebrate Paleontology |volume=40 |pages=e1767638 |doi=10.1080/02724634.2020.1767638 |doi-access=free|bibcode=2020JVPal..40E7638C }}{{cite journal |last=Blanco |first=A. |title=Importance of the postcranial skeleton in eusuchian phylogeny: Reassessing the systematics of allodaposuchid crocodylians |year=2021 |journal=PLoS ONE |volume=16 |issue=6 |page=e0251900 |pmid=34106925 | doi=10.1371/journal.pone.0251900|pmc=8189472 |doi-access=free|bibcode=2021PLoSO..1651900B }} However, molecular studies using DNA sequencing have found the group Brevirostres to be invalid upon finding that crocodiles and gavialids are more closely related than alligators.{{cite journal |pmid=12775527 |year=2003 |last1=Harshman |first1=J. |title=True and false gharials: A nuclear gene phylogeny of crocodylia |journal=Systematic Biology |volume=52 |issue=3 |pages=386–402 |last2=Huddleston |first2=C. J. |last3=Bollback |first3=J. P. |last4=Parsons |first4=T. J. |last5=Braun |first5=M. J. |doi=10.1080/10635150309323 |doi-access=free }}{{cite journal|last1=Gatesy |first1=J. |last2=Amato |first2=G. |year=2008 |title=The rapid accumulation of consistent molecular support for intergeneric crocodylian relationships |journal=Molecular Phylogenetics and Evolution|volume=48 |issue=3 |pages=1232–1237 |doi=10.1016/j.ympev.2008.02.009|pmid=18372192}}{{cite journal| author=Erickson, G. M.| author2=Gignac, P. M.| author3=Steppan, S. J.| author4=Lappin, A. K.| author5=Vliet, K. A.| author6=Brueggen, J. A.| author7=Inouye, B. D.| author8=Kledzik, D.| author9=Webb, G. J. W. | year=2012 | title=Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation | journal=PLOS ONE | volume=7 |issue=3 |page=e31781 |doi=10.1371/journal.pone.0031781|editor1-last=Claessens|editor1-first=Leon|bibcode = 2012PLoSO...731781E | pmid=22431965 | pmc=3303775| doi-access=free}}{{cite journal | author=Michael S. Y. Lee |author2=Adam M. Yates |date=27 June 2018 |title=Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil |journal=Proceedings of the Royal Society B |volume=285 |issue=1881 |doi=10.1098/rspb.2018.1071 |pmid=30051855 |pmc=6030529 |doi-access=free}}{{Cite journal|last1=Hekkala |first1=E. |last2=Gatesy |first2=J. |last3=Narechania |first3=A. |last4=Meredith |first4=R. |last5=Russello |first5=M. |last6=Aardema |first6=M. L. |last7=Jensen |first7=E. |last8=Montanari |first8=S. |last9=Brochu |first9=C. |last10=Norell |first10=M. |last11=Amato |first11=G. |date=2021-04-27 |title=Paleogenomics illuminates the evolutionary history of the extinct Holocene "horned" crocodile of Madagascar, Voay robustus |journal=Communications Biology |language=en |volume=4 |issue=1 |page=505 |doi=10.1038/s42003-021-02017-0 |pmid=33907305 |pmc=8079395 |issn=2399-3642 |doi-access=free}}

A 2018 tip dating study by Lee & Yates using both molecular, morphological and stratigraphic data instead recovered the planocraniids outside crown group Crocodylia. Below is a cladogram from that study:

{{Clade|style=line-height:85%; font-size:85%

|1={{Clade

|1=Goniopholis{{extinct}}

|2={{Clade

|1={{Clade

|1=Bernissartia{{extinct}}

|2=Shamosuchus{{extinct}}

}}

|label2=Eusuchia

|2={{Clade

|1={{Clade

|1=Acynodon{{extinct}}

|label2=Hylaeochampsidae{{extinct}}

|2=Hylaeochampsa{{extinct}}

}}

|2={{Clade

|label1=Allodaposuchidae{{extinct}}

|1={{Clade

|1=Allodaposuchus{{extinct}}

|2=Lohuecosuchus{{extinct}}

}}

|2={{Clade

|1={{Clade

|1=Borealosuchus{{extinct}}

|label2="Thoracosaurs"

|2={{Clade

|1=Eothoracosaurus{{extinct}}

|2={{Clade

|1=Thoracosaurus{{extinct}}

|2={{Clade

|1=Argochampsa{{extinct}}

|2={{Clade

|1=Eogavialis{{extinct}}

|2=Eosuchus{{extinct}}

}} }} }} }} }}

|2={{Clade

|label1=Planocraniidae{{extinct}}

|1={{Clade

|1=Planocrania hengdongensis{{extinct}}

|2={{Clade

|1=Planocrania datangensis{{extinct}}

|2=Boverisuchus{{extinct}}

}} }}

|2=Crocodylia

}} }} }} }} }} }} }}

In 2021, Rio & Mannion conducted a new phylogenetic study using a heavily modified morphological data set, and also noted the lack of consensus and difficulty in placing Planocraniidae. In their study, they recovered Planocraniidae within Crocodylia, as the sister group to Longirostres, as shown in the cladogram below:

{{Clade|style=line-height:85%; font-size:85%

|label1=Eusuchia

|1={{clade

|1=Hylaeochampsidae{{extinct}}

|2={{clade

|1=Allodaposuchidae{{extinct}}

|2={{clade

|1=Borealosuchus{{extinct}}

|label2=Crocodylia

|2={{clade

|1=Alligatoroidea

|2={{clade

|label1=Planocraniidae{{extinct}}

|1={{clade

|1=Planocrania datangensis{{extinct}}

|2={{clade

|1=Planocrania hengdongensis{{extinct}}

|2={{clade

|1=Boverisuchus magnifrons{{extinct}}

|2=Boverisuchus vorax{{extinct}} }} }} }}

|label2=Longirostres

|2={{clade

|1=Gavialoidea

|2=Crocodyloidea }} }} }} }} }} }} }}

File:Skull of Pristichampsus geiseltalensis.JPG of the extinct crocodile “Weigeltisuchus geiseltalensis” KUHN, 1938 (specimen no. GMH Leo X 8001; subsequently “Pristichampsus geiseltalensis”, now referred to Boverisuchus magnifrons KUHN, 1938)]]

Planocraniids were land-living (terrestrial) crocodyliforms with longer legs than living crocodilians. They grew to a maximum size of {{convert|2|to|3|m|ft}} in length.{{cite journal |last=Brochu |first=C. A. |year=2003 |title=Phylogenetic approaches toward crocodylian history |journal=Annual Review of Earth and Planetary Sciences |volume=31 |issue=31 |pages=357–97 |doi=10.1146/annurev.earth.31.100901.141308 |bibcode=2003AREPS..31..357B |url=http://www.naherpetology.org/pdf_files/970.pdf |access-date=2019-05-10 |archive-date=2015-04-02 |archive-url=https://web.archive.org/web/20150402192747/http://www.naherpetology.org/pdf_files/970.pdf |url-status=usurped }} Nearly complete skeletons of Boverisuchus indicate that planocraniids were more heavily armored than living crocodilians, with bony plates called osteoderms tightly interlocking along the back, completely encasing the tail, and extending down the legs. The claws were blunt and have been described as hoof-like in shape,{{Cite journal | last1 = Langston | first1 = W. | title = The Sebecosuchia; cosmopolitan crocodilians? | doi = 10.2475/ajs.254.10.605 | journal = American Journal of Science | volume = 254 | issue = 10 | pages = 605–614 | year = 1956 | doi-access = free | bibcode = 1956AmJS..254..605L }} suggesting that planocraniids may have been unguligrade,{{Cite journal | last1 = Young | first1 = M. T. | last2 = Bell | first2 = M. A. | last3 = Andrade | first3 = M. B. | last4 = Brusatte | first4 = S. L. | title = Body size estimation and evolution in metriorhynchid crocodylomorphs: Implications for species diversification and niche partitioning | doi = 10.1111/j.1096-3642.2011.00734.x | journal = Zoological Journal of the Linnean Society | volume = 163 | issue = 4 | pages = 1199 | year = 2011 | doi-access = free }} walking on the tips of their toes like mammalian ungulates. The areas on the leg bones where muscles attach were in different positions in planocraniids than they are in living crocodilians, possibly as an adaptation to walking on land.

While most crocodilians have flattened skulls, planocraniids had tall and narrow (or laterally compressed) skulls. Their teeth were also laterally compressed and not conical like those of modern crocodilians. The combination of a laterally compressed skull and laterally compressed teeth is called the "ziphodont" condition.

The teeth of the upper jaw completely overlapped the teeth of the lower jaw when the mouth was closed, giving planocraniids an alligator-like overbite. Planocraniids had a notch between the premaxilla bone at the tip of the upper jaw and the maxilla behind it. Living crocodiles also have this notch, which provides room for the enlarged fourth tooth of the lower jaw when the mouth is closed. In planocraniids the fourth tooth was small and did not fit into the notch.

The evolution of Planocraniidae occurred after the K-T extinction when niches were open. Because of the lack of competition, the Planocraniidae evolved to hunt on land, which would have been almost impossible with the dinosaur clades existing.{{Citation|title=Why do Animals Look so Strange After Mass Extinctions|url=https://www.youtube.com/watch?v=1yTAKJFbPFU|language=en|access-date=2021-12-14}}

{{Reflist}}

{{Neosuchia|E.}}

{{Taxonbar|from=Q15076991}}

Category:Neosuchia

Category:Paleocene crocodylomorphs

Category:Terrestrial crocodylomorphs

Category:Paleocene first appearances

Category:Eocene extinctions

Category:Eocene crocodylomorphs

Category:Eocene reptiles of Asia

Category:Eocene reptiles of Europe

Category:Eocene reptiles of North America

Category:Pseudosuchian families