Acynodon

Acynodon
Temporal range: Santonian - Maastrichtian, 86–68 Ma
Skull of Acynodon iberoccitanus (ACAP-FXl)
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Clade: Metasuchia
Clade: Neosuchia
Clade: Eusuchia
Genus: †Acynodon
Buscalioni et al., 1997
Species
  • †A. iberoccitanus Buscalioni et al., 1997 (type)
  • †A. adriaticus Delfino et al., 2008
  • †A. lopezi Buscalioni et al., 1997
Teeth of Acynodon sp. from the Campanian of Villeveyrac, Hérault, France. Max Rouger Collection.

Acynodon is an extinct genus of eusuchian crocodylomorph from the Late Cretaceous, with fossils found throughout Southern Europe.

Classification

The genus Acynodon contains three species: A. iberoccitanus, A. adriaticus, and A. lopezi. Fossils have been found in France, Spain, Italy, and Romania, dating back to the Santonian, Campanian and Maastrichtian periods of the Late Cretaceous.[1] Isolated teeth from the paleontological site of Kozina in Slovenia may be referable to A. adriaticus.[2]

When first described in 1997, it was placed within the family Alligatoridae.[3] New findings a decade later led to it being reclassified as a basal globidontan.[4][1] Recent studies have since resolved Acynodon as a basal eusuchian crocodylomorph, outside of the Crocodylia crown group, and a close relative to Hylaeochampsa.[5][6][7]

Description

The skull of Acynodon is extremely brevirostrine; it had a very short and broad snout compared to other known eusuchians[4], and a specialized muscle arrangement to optimize biting force[8]. Its dentition was quite derived, with the species A. adriaticus bearing extremely enlarged molariform teeth and a lack of maxillary and dentary caniniform teeth, presumably an adaptation to feed on slow prey with hard shells.[1][8] A. adriaticus was highly specialized to durophagy, likely in shallow, densely vegetated waters as suggested by its small orbits, avoiding competition with other sympatric crocodylomorphs like the generalist Allodaposuchus or the terrestrial Doratodon[2]. It had an acute lateral snout profile in comparison to the more rounded shape of A. iberoccitanus.[8] A. adriaticus is the only species preserving articulated postcranial material in at least two specimens. These show the typical semiacquatic proportions and paravertebral osteoderms bearing a distinctively double-keel[1][9]. Histological thin sections of a specimen's dorsal rib show a thickened cortical layer, possibly associated with strong aquatic adaptations, and at least 31 Lines of Arrested Growth (LAGs) despite the specimen being a somatically immature individual. This suggests that the species was relatively long lived and underwent a steady slow growth.[9]

References

  1. ^ a b c d Delfino, M.; Martin, J. E.; Buffetaut, E. (2008). "A new species of Acynodon (Crocodylia) from the Upper Cretaceous (Santonian-Campanian) of Villaggio del Pescatore, Italy". Palaeontology. 51 (5): 1091–1106. Bibcode:2008Palgy..51.1091D. doi:10.1111/j.1475-4983.2008.00800.x.
  2. ^ a b Muscioni, Marco; Chiarenza, Alfio Alessandro; Nicholl, Cecily S C; Perentin, Tullio; Dreossi, Diego; Fanti, Federico (2025-12-01). "A ziphodont crocodylomorph from Villaggio del Pescatore Lagerstätte (Campanian, Italy)". Zoological Journal of the Linnean Society. 205 (4). doi:10.1093/zoolinnean/zlaf171. ISSN 0024-4082.
  3. ^ Buscalioni, A. D.; Ortega, F. L.; Vasse, D. (1997). "New crocodiles (Eusuchia: Alligatoroidea) from the Upper Cretaceous of southern Europe". Comptes Rendus de l'Académie des Sciences, Série IIA. 325 (7): 525–530. Bibcode:1997CRASE.325..525B. doi:10.1016/s1251-8050(97)89872-2.
  4. ^ a b Martin, J. E. (2007). "New material of the Late Cretaceous globidontan Acynodon iberoccitanus (crocodylia) from Southern France". Journal of Vertebrate Paleontology. 27 (2): 362–372. doi:10.1671/0272-4634(2007)27[362:NMOTLC]2.0.CO;2. S2CID 130433177.
  5. ^ 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". Proceedings of the Royal Society B. 285 (1881). doi:10.1098/rspb.2018.1071. PMC 6030529. PMID 30051855.
  6. ^ Tobias Massonne; Davit Vasilyan; Márton Rabi; Madelaine Böhme (2019). "A new alligatoroid from the Eocene of Vietnam highlights an extinct Asian clade independent from extant Alligator sinensis". PeerJ. 7 e7562. doi:10.7717/peerj.7562. PMC 6839522. PMID 31720094.
  7. ^ Blanco, A. (2021). "Importance of the postcranial skeleton in eusuchian phylogeny: Reassessing the systematics of allodaposuchid crocodylians". PLOS ONE. 16 (6) e0251900. Bibcode:2021PLoSO..1651900B. doi:10.1371/journal.pone.0251900. PMC 8189472. PMID 34106925.
  8. ^ a b c Muscioni, Marco; Chiarenza, Alfio Alessandro; Fernandez, Diego Bladimir Haro; Dreossi, Diego; Bacchia, Flavio; Fanti, Federico (2024-09-12). "Cranial anatomy of Acynodon adriaticus and extreme durophagous adaptations in Eusuchia (Reptilia: Crocodylomorpha)". The Anatomical Record. doi:10.1002/ar.25574. hdl:11585/995756. ISSN 1932-8486.
  9. ^ a b Marco, Muscioni; Chiarenza, Alfio Alessandro; Delfino, Massimo; Fabbri, Matteo; Milocco, Kevin; Fanti, Federico (2023-11-01). "Acynodon adriaticus from Villaggio del Pescatore (Campanian of Italy): Anatomical and chronostratigraphic integration improves phylogenetic resolution in Hylaeochampsidae (Eusuchia)". Cretaceous Research. 151: 105631. doi:10.1016/j.cretres.2023.105631. ISSN 0195-6671.{{cite journal}}: CS1 maint: article number as page number (link)
allikas: https://en.wikipedia.org/wiki/Acynodon_iberoccitanus