化石研究会会誌

Journal of Fossil Research, Vol. 54（1）, 11-14（２０21）［Note］

Reappraisal of a supposed chalicotheriid perissodactyl femur
from the Pliocene of Yenangyoung, central Myanmar
Naoto Handa* and Takehisa Tsubamoto**, ***Neogene vertebrate fossils from Myanmar havebeen reported since early 19th century (Clift 1828 ;Falconer 1868 ; Lydekker 1883 ; Noetling 1894, 1895,1897a, 1897b, 1901). More recently, many more Neogene

Systematic paleontology
Family Chalicotheriidae Gill, 1872
Subfamily Schizotheriinae Holland and Peterson, 1914
Schizotheriinae indeterminate

vertebrate fossils have been reported and describedfrom Myanmar (Colbert 1935, 1938 ; Nishioka and Takai
2018 ; Takai et al. 2018a, 2018b ; Nishioka et al. 2018 ;Egi et al. 2018 ; Saegusa 2018 ; and references therein).
Among the early studies, Noetling (1895) reported thediscovery of a femur of a large mammal from theNeogene at Yenangyoung, central Myanmar, andpreliminarily identified it as Rhinoceros sp. (Perissodactyla,Rhinocerotidae). Then, Noetling (1897a) described thisleft femur and identified it as Hippopotamus irravadicus(Artiodactyla, Hippopotamidae). Later, Hooijer (1951) 
restudied this specimen and concluded that it appeared
to be a chalicotheriid perissodactyl femur. He mentionedthat the specimen would be the first record of thefamily in Myanmar. However, this taxonomic assignment
has not been confirmed since then. Here, we reappraise
this fossil femur and demonstrate its familial andsubfamilial affinities on the basis of the figures by
Noetling (1897a). Unfortunately, Noetling did not specify
a repository or specimen number and therefore wecannot access the specimen itself.
Fig. 1. S chizotheriinae indeterminate, a left femur originally describedfrom the Pliocene of Myanmar by Noetling (1897a). A,anterior view. B, posterior view. C, distal view. A–C, redrawn
after Noetling (1897a).

Received :  25 February, 2021 ; Accepted : 6 June, 2021  *Faculty of Humanities and Social Sciences, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo
192-0397, Japan   Email : k1552325@kadai.jp**Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan   Email : tsubamoto@sci.ehime-u.ac.jp***Corresponding author
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Material.—A left femur originally described as

Hippopotamus irravadicus by Noetling (1897a, plate XIX :figs. 1, 1a ; plate XX : fig. 1).

is developed and proximodistally high ; the apex of thegreater trochanter projects proximally ; the lesser
trochanter is weakly developed ; the third trochanter

Repository and specimen number.—Unknown

is thin and is situated on the proximal side of the shaft ;(Noetling 1897a ; Hooijer 1951). However, the specimen

and the keels of the femoral trochlea are almost parallel

is likely stored in the Geological Survey of India (Kolkata,India) because Dr. Noetling was a paleontologist inwith a shallow groove. These characteristics are seenin schizotheriine femora (Handa and Kawabe 2016).

this institute at that time (Noetling 1894, 1895, 1897a,

Several femora of the Schizotheriinae have been described

1897b, 1901).

from North America and Eurasia. The weak lesser

Locality.—Yenangyoung (= Yenangyaung),
Magway Division, central Myanmar (Noetling 1897a ;trochanter of the studied femur is distinguished fromthose of Moropus, Tylocephalonyx, Metaschizotherium andHorizon and age.—A ferruginous conglomeratic

Ancylotherium (Coombs 1978, 1979 ; Roussiakis andTheodorou 2001). A femur of an indeterminate

layer of the Irrawaddy sediments (Noetling 1897a,schizotheriine species was found from the lower Miocene1897b) ; early Pliocene according to Noetling (1897a),of Japan (Handa and Kawabe 2016). The studied femur

but likely mid-Pliocene to late Pliocene according toHooijer (1951).
Measurements.—The femur length (from thefrom Myanmar is distinguished from this Japanese

Hooijer 1951).

schizotheriine femur in having a weak lesser trochanterand the weakness of the third trochanter.

middle of the distal condyles to the top of the greatertrochanter) is about 60 cm (Noetling 1897a).

The femur from Myanmar is distinguished fromthat of the other subfamily Chalicotheriinae of theComparisons.—This femur is large among mammals
and has a third trochanter, indicating that it is assigned
to the Perissodactyla. The femur is relatively long,implying that it should be assigned to the Rhinocerotidae
or Chalicotheriidae.

Chalicotheriidae. Femora of the other subfamily

Chalicotheriinae, such as those of Anisodon grande (deBlainville, 1849), have only faintly developed lesser
and third trochanters (Zapfe 1979 ; Guérin 2012). Thesecharacters are not seen in this femur. In addition, theThis femur is distinguished from that of theRhinocerotidae in having a proximodistally high greater
trochanter, a third trochanter on the proximal portion

femur length of A. grande is shorter than that of thisfemur (Zapfe 1979 ; Guérin 2012). Therefore, this femur
is distinguished from the Chalicotheriinae.

of the lateral side of the shaft, and a moderately small

In sum, this femur is assigned to the Schizotheriinae

sized trochlea and almost parallel keels of the trochlea(Perissodactyla, Chalicotheriidae). Its generic identificationin dorsal view (see Handa and Kawabe 2016 andis difficult due to the lack of other important skeletal

references therein). The third trochanter of the studied

elements such as cranio-mandibles and teeth.

femur appears to be developed extremely weakly,Remarks.—In Myanmar, the fossil record of thealthough it might be partially broken. If this condition

Chalicotheriidae is poorly known, and only someis natural, the studied femur also differs from that ofgnathodental remains of the subfamily Chalicotheriinae

the Rhinocerotidae in having a weak third trochanter.

have been described so far. Tsubamoto et al. (2006) 

The studied femur is larger than those of most of thedescribed fragmentary upper and lower molars of theextinct and extant Rhinocerotidae (see Guérin 1980).

Chalicotheriine from the upper part of the Irrawaddy

The femoral length of the Indian rhino, Rhinoceros
unicornis, is comparable to that of the studied femur

sediments at the Gwebin locality (likely late Pliocene ;Tsubamoto et al. 2012 ; Takai et al. 2018b), Seikpyu(Guérin 1980). However, the studied femur differs from

Township, Magway Division. They provisionally identified

greater trochanter and a more proximally situatedgeneric affinity is still uncertain due to the incompletenessthe femur of R. unicornis in having a proximally projected

the specimens as cf. Nestoritherium sp., although their

third trochanter. Therefore, it is likely assigned to theof the fossil material. Chavasseau et al. (2010) described

Chalicotheriidae.
Among the Chalicotheriidae, this femur is closely

a left mandibular fragment with p3–m1 of theChalicotheriinae from the upper Miocene part of thecomparable to the subfamily Schizotheriinae in having

Irrawaddy sediments near Magway, Magway Division.

the following characteristics : the greater trochanter

Later, Chen et al. (2016) assigned this specimen to a─ 12 ─chalicotheriine species, Anisodon yuanmouensis (Gao andMa, 1997). Chit-Sein and Tin-Thein (2013) also describeda right mandibular fragment with m1 from the Tebingan

Chit-Sein, Tin-Thein （2013） A new record of Chalicotherium
from the Irrawaddy Formation in Migyaungye Area,
Magway Region. Universities Research Journal 6,207-218

locality, Magway Division, and assigned it to achalicotheriine species, Chalicotherium salinum (Forster-Cooper, 1922) (= Anisodon salinus). Nishioka et al. (2018) 
reported a discovery of a chalicotheriine (low-crowned) Clift W （1828） On the fossil remains of two new speciesof Mastodon, and other vertebrated animals, foundon the left Bank of the Irawadi. Transactions of theright lower molar from the uppermost Miocene/lower

Geological Society of London （Series 2） 2（3）, 369‒375

Pliocene part of the Irrawaddy sediments at theColbert EH （1935） Siwalik mammals in the American

Chaingzauk locality, Pauk Township, Magway Division.
first record of the Schizotheriinae in Myanmar, although

Museum of Natural History. Transactions of theAmerican Philosophical Society （New Series） 26,1401

additional fossils are necessary to completely confirm

Colbert EH （1938） Fossil mammals from Burma in thethe presence of this subfamily in the Neogene of Myanmar.

American Museum of Natural History. Bulletin ofSeveral Plio-Pleistocene schizotheriine are known

the American Museum of Natural History 74, 255-436

from Kenya, Uganda, Ethiopia, Tanzania and SouthCoombs MC （1978） Reevaluation of early Miocene
North American Moropus （Perissodactyla,Therefore, the femur in the present study would be

Africa (Coombs and Cote 2010) and China (Gansu andShaanxi provinces) (Li and Deng 2003 ; Chen et al.
2012), but their fossil records are still insufficientcompared with the Miocene records. Additional discovery
of Plio-Pleistocene schizotheriine specimens in theIrrawaddy sediments contributes to the discussion ofthe paleobiogeography and evolution of Afro-Eurasianschizotheriines.

Chalicotheriidae, Schizotheriinae）. Bulletin of Carnegie

Museum of Natural History 4, 1-62
Coombs MC （1979） Tylocephalonyx, a new genus ofNorth American dome-skulled chalicotheres （Mammalia,Perissodactyla）. Bulletin of the American Museumof Natural History 164, 1-64
Coombs MC, Cote, SM （2010） Chalicotheriidae. In :Werdelin L, Sanders WJ （eds.） Cenozoic Mammals

Acknowledgments
JSPS KAKENHI Grant Numbers 15K05330 and 18H01327

of Africa, University of California Press, Berkeley,659-667
de Blainville HMD （1849） BB. Des Anoplothériums

to Naoko Egi. This manuscript was improved by the（G. Cuvier）. In : de Blainville HMD （ed） Ostéographie

constructive reviews by Margery Coombs (Universityou description iconographique comparée du squeletteof Massachusetts, Amherst, USA) and Christopheet du système dentaire des Mammifères récents etMallet (Museum National d'Histoire naturelle, Paris,France).
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