Diplocynodon is anextinctgenus ofeusuchian, either analligatoroidcrocodilian or a stem-group crocodilian, that lived during thePaleocene toMiddle Miocene inEurope. Some species may have reached lengths of 3 metres (9.8 ft),[7] while others probably did not exceed 1 metre (3.3 ft).[8] They are almost exclusively found in freshwater environments.[9] The various species are thought to have been opportunistic aquatic predators.[10]
In the nineteenth century,D. steineri was named fromStyria,Austria andD. styriacus was named fromAustria andFrance. A third Austrian species,Enneodon ungeri, was placed in its own genus. The Austrian and French species ofDiplocynodon weresynonymized withE. ungeri in 2011, and because the nameDiplocynodon has priority overEnneodon, the species is now calledD. ungeri.[11] Othergenera have recently been found to besynonymous withDiplocynodon.Hispanochampsa muelleri of Spain was determined to be synonymous withDiplocynodon in 2006,[5] andBaryphracta deponaie of Germany was confirmed to be synonymous withDiplocynodon in 2012.[3]
Well preserved specimens have been found in theMessel Pit and theGeiseltallignite deposit inGermany. Most articulatedDiplocynodon specimens from these localities containgastroliths. In theEocene epoch, the German sites were either a swampy freshwater lake (Messel Pit) or a peat bog swamp (Geiseltal).
Below is a more detailedcladogram ofDiplocynodon:[14]
Diplocynodon
Diplocynodon deponiae
Diplocynodon darwini
Diplocynodon hantoniensis
Diplocynodon ratelii
Diplocynodon tormis
Diplocynodon muelleri
In a 2025 study, Jules D. Walter and colleagues argue that many character states previously thought to be diagnostic for alligatoroids were actually much more widespread. In their analysis several genera traditionally viewed as basal alligatoroids, among themDiplocynodon, were found to not only fall outside of Alligatoroidea but to not even be true crocodilians, instead representing derived non-crocodilian eusuchians.[15]
Osteohistological analysis ofD. hantoniensis suggests that it had a similar pattern of growth to the modernAmerican alligator, exhibiting a determinate, seasonally-controlled rate of growth. Additionally,D. hantoniensis was allometrically very similar to American alligators, with the femoral length and femoral circumference scaling in a similar fashion in both species.[16]
CT scans ofD. tormis reconstruct internal structures of its snout and a portion of its brain, with implications for its sensory and cognitive capabilities. The relative sizes of theolfactory bulbs overlap with alligatoroids and fall short of true crocodiles, adding to anatomical evidence for a closer relationship to alligatoroids. Theoptic lobes andreptile encephalization quotient are proportionally smaller than other medium-sized crocodilians, though this could be influenced by incomplete preservation at the back of the skull.[17]
Based on skull shape analysis of the crocodylians known from theLutetian site of Geiseltal,Diplocynodon was a small generalist carnivore that partitioned its resources with the largerAsiatosuchus.[18] According to enamelδ13C values from specimens from theLate Oligocene site of Enspel, theDiplocynodon living in the palaeoenvironment fed primarily on aquatic vertebrates.[19]
^abcRossmann, T.; Blume, M. (1999). "Die Krokodil-Fauna der Fossillagerstätte Grube Messel".Ein aktueller Überblick., Natur und Museum, Frankfurt am Main.129 (9):261–270.
^abcdMassimo Delfino; Thierry Smith (2012). "Reappraisal of the morphology and phylogenetic relationships of the middle Eocene alligatoroidDiplocynodon deponiae (Frey, Laemmert, and Riess, 1987) based on a three-dimensional specimen".Journal of Vertebrate Paleontology.32 (6):1358–1369.Bibcode:2012JVPal..32.1358D.doi:10.1080/02724634.2012.699484.S2CID84977303.
^Sabău I, Venczel M, Codrea VA, Bordeianu M. 2021.Diplocynodon: a salt water eocene crocodile from Transylvania? North-Western Journal of Zoology 17(1):117-121
^abJeremy E. Martin; Martin Gross (2011). "Taxonomic clarification ofDiplocynodon Pomel, 1847 (Crocodilia) from the Miocene of Styria, Austria".Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen.261 (2):177–193.doi:10.1127/0077-7749/2011/0159.
^Jeremy E. Martin (2010). "A new species ofDiplocynodon (Crocodylia, Alligatoroidea) from the Late Eocene of the Massif Central, France, and the evolution of the genus in the climatic context of the Late Palaeogene".Geological Magazine.147 (4):596–610.Bibcode:2010GeoM..147..596M.doi:10.1017/S0016756809990161.S2CID140593139.
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