Gigantic Otter Discovered with Implications for Otter Evolution

A new otter of giant size, Sigmogale melilutra sp. Nov. (Lutrinae: Mustelidae: Carnivora), from the latest Miocene Shuitangba site in north-eastern Yunnan, south-western China, and a total-evidence phylogeny of lutrines

Xiaoming Wang, Camille Grohé, Denise F. Su, Stuart C. White, Xueping Ji, Jay Kelley, Nina G. Jablonski, Tao Deng, Youshan You, and Xin Yang

Data: These authors found an entire skull, jaw fragments, and parts of skeletons of three new species of otter. This otter has a skull length (snout to back of head) of about 385 mm, for comparison the length of a human skull is about 200 mm.

This is the skull of the new species, Siamogale melilutra. The specimen is the holotype from Shuitangba, number ZT-10-03-064b. This is Figure 3 in the paper.
This is the skull of the new species, Siamogale melilutra. The specimen is the holotype from Shuitangba, number ZT-10-03-064b. This is Figure 3 in the paper.

Methods: They used computed tomography (CT) scanning uses special X-rays to create detailed scans. In this study, it was used in order to reconstruct the crushed skull. CT scanning allows for virtual fossils to be created, which makes manipulating and handling the fossil much easier. There is less chance to accidentally break the fossils, which can be quite delicate. The paleontologists could then critically examine the new skull and compare it to the already understood otter skull to make statements about relationships between the new species and species that have already been discovered.

Results and Importance: After reconstructing the crushed skull the authors of the study found similarities between this skull and modern beavers and otters, such as aspects of the skull and teeth, as well as other openings in the skull. There has been disagreements between paleontologists as to the placement of otters within the larger tree of life. Different studies using different methods have obtained different results. This published study provides the first total evidence (both morphology and molecular data) evolutionary history of otters. This work suggests that a certain group of otters is not actually a natural group, but rather an early representative at the origins of the European and North American otters.

This new discovery allows for a better understanding of previously found fossils by comparing these strange fragmented bone materials to other mostly complete skulls to understand relatedness. These fragments are often labeled “badger” or “otter” with little other descriptions. This specimen shares features of both the badger and otter groups, making it a very interesting organism.

The Big Picture: By better studying these evolutionary relationships, paleontologists can now use the refined otter branch on the tree of life as a framework to assess various processes. Specifically, there appears to be large implications for speciation and biogeographic (what species lived where, and why) trends in this group. The distance between certain locations of specimens discovered implies that these large otters were very good at crossing barriers (such as rivers) that often restrict movement of groups.

This is an artist’s (Mauricio Antón) reconstruction of a habitat that would have contained this large otter and some similar animals and plants for the time period. This is Figure 12 in the paper.
This is an artist’s (Mauricio Antón) reconstruction of a habitat that would have contained this large otter and some similar animals and plants for the time period. This is Figure 12 in the paper.

Citation: Xiaoming Wang, Camille Grohé, Denise F. Su, Stuart C. White, Xueping Ji, Jay Kelley, Nina G. Jablonski, Tao Deng, Youshan You, and Xin Yang (2017): A new otter of giant size, Sigmogale melilutra sp. Nov. (Lutrinae: Mustelidae: Carnivora), from the latest Miocene Shuitangba site in north-eastern Yunnan, south-western China, and a total-evidence phylogeny of lutrines. Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2016.1267666

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