Planocrania Explained

Planocrania is an extinct genus of eusuchian crocodyliforms from what is now China.^[1] Two species are currently known to belong to the genus.

History

The type species, Planocrania datangensis, was named in 1976 from material found from Nanxiong in Guangdong Province, China, and the new genus Planocrania was placed in a newly erected family Planocraniidae.^[2] A second species, Planocrania hengdongensis, is known from Hengdong County in Hunan Province and was described in 1984.^[3]

Planocrania was subsequently included in the family Pristichampsidae along with the genus Pristichampsus. Both genera were previously assigned to the subfamily Pristichampsinae within the family Crocodylidae before they were placed in their own family, the Pristichampsidae.^[4]

However, in a 2013 phylogenetic analysis, the two Asian species of Planocrania were found to be most closely related to the North American and European Boverisuchus, and the family Planocraniidae was reinstated to contain these genera and replace Pristichampsidae.^[5]

Phylogeny

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.^{[5] [6] [7]} 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.^{[8] [9] [10] [1] [11]}

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:^[1]

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:

Notes and References

1. Michael S. Y. Lee . Adam M. Yates . 27 June 2018 . Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil . . 285 . 1881 . 10.1098/rspb.2018.1071 . 30051855 . 6030529 . free.
2. Li . J. L. . 1976 . Fossils of Sebecosuchia discovered from Nanxiong, Guangdong . Vertebrata PalAsiatica . 14 . 169–173.
3. Li . J. L. . 1984 . A new species of Planocrania from Hengdong, Hunan . Vertebrata PalAsiatica . 22 . 2 . 123–134.
4. Brochu . C. A. . 2001 . Crocodylian snouts in space and time: phylogenetic approaches toward adaptive radiation . American Zoologist . 41 . 3 . 564–585 . 10.1668/0003-1569(2001)041[0564:CSISAT]2.0.CO;2. 198156966 . 10.1.1.554.231 .
5. Brochu . C. A. . Phylogenetic relationships of Palaeogene ziphodont eusuchians and the status of Pristichampsus Gervais, 1853 . 10.1017/S1755691013000200 . Earth and Environmental Science Transactions of the Royal Society of Edinburgh . 521–550 . 2013 . 103 . 3–4 . 128920027 .
6. Adam P. Cossette . Christopher A. Brochu . 2020 . 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 . . 40 . e1767638 . 10.1080/02724634.2020.1767638 . free.
7. Blanco . A. . Importance of the postcranial skeleton in eusuchian phylogeny: Reassessing the systematics of allodaposuchid crocodylians . 2021 . . 16 . 6 . e0251900 . 34106925. 10.1371/journal.pone.0251900 . 8189472 . free.
8. 12775527 . 2003 . Harshman . J. . True and false gharials: A nuclear gene phylogeny of crocodylia . Systematic Biology . 52. 3. 386–402. Huddleston. C. J. . Bollback . J. P. . Parsons. T. J.. Braun. M. J.. 10.1080/10635150309323 . free .
9. Gatesy . J. . Amato . G. . 2008 . The rapid accumulation of consistent molecular support for intergeneric crocodylian relationships . Molecular Phylogenetics and Evolution. 48 . 3 . 1232–1237 . 10.1016/j.ympev.2008.02.009. 18372192.
10. Erickson, G. M.. Gignac, P. M.. Steppan, S. J.. Lappin, A. K.. Vliet, K. A.. Brueggen, J. A.. Inouye, B. D.. Kledzik, D.. Webb, G. J. W. . 2012 . Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation . PLOS ONE . 7 . 3 . e31781 . 10.1371/journal.pone.0031781. Claessens. Leon. 2012PLoSO...731781E . 22431965 . 3303775. free.
11. Hekkala . E. . Gatesy . J. . Narechania . A. . Meredith . R. . Russello . M. . Aardema . M. L. . Jensen . E. . Montanari . S. . Brochu . C. . Norell . M. . Amato . G. . 2021-04-27 . Paleogenomics illuminates the evolutionary history of the extinct Holocene "horned" crocodile of Madagascar, Voay robustus . Communications Biology . en . 4 . 1 . 505 . 10.1038/s42003-021-02017-0 . 33907305 . 8079395 . 2399-3642 . free.