''Milosaurus'' is an extinct
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of non-
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
ian
synapsid
Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...
s native to
Illinois
Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...
that was alive during the
latest Carboniferous and
earliest Permian. It was named in 1970 on the basis of FMNH 701, a partial skeleton, as well as referred material.
[R. DeMar. 1970. A primitive pelycosaur from the Pennsylvanian of Illinois. ''Journal of Paleontology'' 44(1):154-163]
Discovery
The
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
of ''Milosaurus'' was found in the Falmouth locality in
Jasper County, Illinois. At the time, the discovery was only the second
sphenacodont found in Illinois, the first being ''
Macromerion''.
Since then the assignment of ''Milosaurus'' to Sphenacodontia has been refuted.
The name ''Milosaurus'' ''mccordi'' refers to Milo Flynn and Chester McCord, the men on whose property the fossils were found.
The material recovered from the area includes the holotype, which consists of a pelvis, hind limb and pes, and caudal vertebrae. Referred material from nearby was also recovered and were thought to possibly be from the same individual which consisted of a lumbar vertebra, a neural spine, a "rib", and a piece of maxilla with teeth.
The validity of this referred material has been debated.
The main reason this material was referred to ''Milosaurus'' was because at the time there had been no other known synapsid discoveries in the area, leading to the assumption that all discovered material belonged to ''Milosaurus''.
However, since the 1970 publication, an undescribed neural spine that belongs to an
edaphosaurid has been found in the area.
Additionally, the maxilla and poorly-described neural arch have since been lost.
The "rib" was later identified as actually being a femur much smaller than the holotype, indicating it may be from a juvenile ''Milosaurus''.
Description
''Milosaurus'' was one of the largest synapsids of its time, estimated to have weighed around 41 kilograms. It may be a third example of large body size developing in synapsids in the Carboniferous, the other two instances being herbivorous edaphosaurids and then sphenacodontids.
Like its close relative ''
Ianthodon'', it would likely have a relatively tall snout and, as is common for early non-mammalian synapsids, a sprawling posture.
Classification
''Milosaurus'' was recovered within the Haptodontiformes which currently includes ''Ianthodon.'' However, due to the known material of ''Milosaurus'' and ''Ianthodon'', it is impossible to determine their relationship to each other. ''Milosaurus'' can confidently be placed outside of the clade containing Edaphosauridae and Sphenacodontia because of the lack of a anterodorsal expansion on its ilium and the presence of a groove on its dorsal surface.
See also
*
List of pelycosaurs
References
Eupelycosauria
Carboniferous synapsids of North America
Cisuralian synapsids of North America
Fossil taxa described in 1970
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