ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)

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Late Pleistocene tiger fossils from the Shiriyazaki on the Shimokita Peninsula northern Honshu, Japan

This is a comparative report on Shiriyazaki's Japanese Late Pleistocene tiger fossils published last year.Although many previous reports on Japanese tiger fossils were very small, the tiger fossils collected in this report are all very large, with an overall size equivalent to that of male Amur tiger, and even some individuals significantly larger

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Fossils were collected from different locations in Shiriyazaki, involving dental materials and limb bone materials. I have selected some materials to discuss, and more materials can be found in the original text:

<下北半島尻屋崎地域産トラ化石> 
Bull.Gunma Mus.Natu.Hist.（28）：45－64, 2024.

1.Comparative materials

The comparative material is an elderly male Amur tiger, born in Germany in 1992. The male Amur tiger was kept in Hamamatsu Zoo(浜松市動物園) from 1995 to 2010 at the age of 18. The cause of death is believed to be related to
lymphadenopathy. "Name: ルー(Lu), International Lineage Registration Number: 3920

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This individual has a very large skull(380mm×284mm) and an overall limb bone length comparable to other male Amur tiger individuals (Tiger-04, AMNH85404, AMNH85396,M.S.241/M.S.242).

2.Upper canine

These three canine teeth are all very large. The translation of the relevant measurement indicators: 
全長=total length
歯冠前後径=anteroposterior diameter of crown base
歯冠頰舌径=lateromedial diameter (buccal lingual side) of crown base
歯冠高さ（頰側）=crown height (buccal)
歯根最大前後径=maximum anteroposterior diameter of tooth root
歯根最大頰舌径=maximum lateromedial diameter of tooth root

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The main text does not provide a comparison between them and Amur tigers. Here, I use Boneclones' Amur tiger skull as a substitute for comparison. The measurements are shown below

歯冠前後径:26.9mm(L) 26.6mm®
歯冠類舌径:20.4mm
歯冠高さ（頰側):58.9mm(L) 58.3mm®

I don't have root measurement data for male Amur tigers, but considering they are larger than the largest root measurement data (31mm) among dozens of male South African lions in Smuts' article[<Age determination of the African lion (Pantheva leo) >], their size is indeed very large.The relatively small crown height may be due to individual developmental differences and taphonomy influences (see figure), and overall, these canine are undoubtedly the size of male Amur

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Other premolar materials show individual variations in the development of the anterior cusp and the boundary morphology of the labial and buccal sides, with overall measurements similar to those of Amur tigers

3.Appendicular skeleton

In terms of overall size, these tiger appendicular bone fossils are almost the same size as those of "ルー", with only a few individuals slightly smaller (such as NMNS9621).But many Appendicular skeleton elements, such as the femur, are proportionally more robust than "ルー", which may be due to the lack of activity in captive individuals.

Impressively, there is a large incomplete humerus and it's maximum distal width(内顆・外顆間の幅) is 97mm.The lateromedial diameter and anteroposterior diameter at the end of the deltoid crest are 35mm and 43mm, respectively, and the bone is very thick and robust.

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There is a record of a very large tiger humerus in Gross 1992, with a maximum length of 373mm and a maximum distal width of 96mm, almost the same width as this incomplete humerus.And a robust watualang tiger humerus(NM1933,353mm greatest length and 99mm distal width ) also have the similar width.

There is another extremely large individual worth mentioning:NMNS25891(5th metatarsus).

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The measurement values of all aspects of this Mt5 material are larger than "ルー", and the difference in length is more significant (132vs118). its overall size should be comparable to the elderly male cave lion in Siegsdorf (132.5mm, Gross 1992:127). Specifically, this cave lion is a medium-sized individual of the Late Pleistocene European cave lion.

Summary

The tigers in this region during the late Pleistocene were very large, with an overall size similar to that of male Amur tigers, and some individuals slightly smaller, possibly due to sexual or individual differences (size differences are not particularly significant compared to "ルー"). 

There are also some very large individuals among them, whose Appendicular skeleton elements are much larger in size than the normal male Amur tiger, reaching the size of a medium-sized cave lion.It is worth noting that there are also reports of giant wolf and brown bear fossils in this area Reply