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| Crocodylus halli Murray, Russo, Zorrilla & McMahan, 2019 |
Abstract
The freshwater crocodile inhabiting Papua New Guinea, currently recognized as Crocodylus novaeguineae, exhibits morphological, molecular, and ecological divergence between the northern and southern versants of the Central Highlands and occupies separate evolutionary trajectories. A robust body of work has long encouraged the formal description of New Guinea crocodiles from the southern versant of the highlands as a distinct lineage with a taxonomy that reflects diagnosed relationships. Here, we use geometric morphometric techniques to assess cranial shape variation between specimens from both versants and add to the diagnostic evidence supporting a more accurate taxonomy. Further, herein, we formally describe the southern variant as a distinct lineage (Hall's New Guinea Crocodile; Crocodylus halli, new species).
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| Ventral cranial shape variation with corresponding example specimen among drainages in Papua New Guinea. Populations in northern drainages (i.e., Sepik; FMNH 14048; Crocodylus novaeguineae) exhibit an extended maxilla and reduced postcranial elements relative to southern populations from Lake Murray/Binaturi ( Crocodylus halli; LSUMZ 44740) and the Aramia River (C. halli; USNM 211290), exhibiting strikingly shorter maxilla and enlarged postcranial elements. |
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| Fig. 7: Holotype of Crocodylus halli, USNM 211290. |
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| Fig. 6: Live individual of Crocodylus halli at St. Augustine Alligator Farm Zoological Park. |
Crocodylus halli, new species
urn:lsid:zoobank.org:act:2B819FD7-B74C-42B4-A85B-7D4B93D96105
Hall's New Guinea Crocodile
Diagnosis.— Crocodylus halli is readily separated from C. novaeguineae based on a longer frontal bone (versus shorter in C. novaeguineae); a shorter maxilla and nasal (versus longer in C.novaeguineae); long and wide postorbital and squamosal (versus short and narrow in C.novaeguineae); and a wider palatine of pterygoid that extends posteriorly (versus narrow and medially oriented in C. novaeguineae). Additionally, C. halli possesses no more than four non-contiguous post-occipital scutes, versus four to six contiguous post-occipital scutes in C. novaeguineae.
Species description and variation.— Variation in morphology of adult Crocodylus halli exists among drainages, with specimens from Lake Murray exhibiting a skull width that is more than half of the skull length (posteromedial squamosal to anteromedial premaxilla), resulting in the appearance of a stocky and wide head in adults. Specimens from Aramia River have generally longer maxilla and shorter postcranial elements than Lake Murray individuals, while maintaining shorter maxilla and longer postcranial elements than C. novaeguineae. Juveniles retain morphology consistent with ontogenetic constraints, exhibiting a relatively enlarged orbit and compressed postcranial elements.
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| Fig. 2: Map of localities for specimens examined; Crocodylus novaeguineae from the Sepik (circle) and Hunstein (pentagon) drainages, and Crocodylus halli from Lake Murray (square), Binaturi (triangle), and Aramia (star) rivers. |
Distribution.— Crocodylus halli occurs within drainages south of the Central Highlands of Papua New Guinea in swamps, rivers, lakes, and occasionally estuaries.
Natural history.— Females of C. halli nest in the rainy season (November–April) and lay larger eggs in smaller clutches than C. novaeguineae, which nests near end of the dry season (July–November; Cox, 1985; Hall, 1985; Hall and Johnson, 1987).
Etymology.— The specific epithet recognizes the fieldwork and research of Philip Hall whose contributions provided the initial framework for supporting distinctiveness of this species.
Christopher M. Murray, Peter Russo, Alexander Zorrilla and Caleb D. McMahan. 2019. Divergent Morphology among Populations of the New Guinea Crocodile, Crocodylus novaeguineae (Schmidt, 1928): Diagnosis of An Independent Lineage and Description of A New Species. Copeia. 107(3); 517-523. DOI: 10.1643/CG-19-240
