''Yalkaparidon'' is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus of
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
n
marsupials, first described in 1988 and known only from the
Oligo-
Miocene deposits of
Riversleigh, northwestern
Queensland, Australia.
Species
Two
species, ''Y. coheni'' and ''Y. jonesi'', have so far been described. Numerous isolated teeth and
jaw bones of ''Yalkaparidon'' are known, but only a single
skull (of ''Y. coheni'') has so far been recovered.
Etymology
The generic name ''Yalkaparidon'' comes from an
aboriginal
Aborigine, aborigine or aboriginal may refer to:
*Aborigines (mythology), in Roman mythology
* Indigenous peoples, general term for ethnic groups who are the earliest known inhabitants of an area
*One of several groups of indigenous peoples, see ...
word for
boomerang, alluding to the boomerang-like shape of its
molars when seen in occlusal view, and the Greek word for tooth.
Characteristics and classification
These specimens of ''Yalkaparidon'' exhibit a melange of characters: the molars are
zalambdodont (a distinctive
tooth type also found in the marsupial mole ''
Notoryctes'', the living placental '
insectivore
A robber fly eating a hoverfly
An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects.
The first vertebrate insectivores wer ...
s' ''
Solenodon'',
tenrecs and
golden moles, as well as a number of
fossil groups); the
incisors are very large and hypselodont (open-rooted and hence ever-growing, similar to those of
rodents); the basicranial region of the only known skull is very primitive, somewhat similar to those of
plesiomorphic
In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades.
Plesiomorphy, symplesiomorphy, apomorphy, and ...
bandicoots. The zalambdodont molars appear to link it to notoryctid marsupial moles, but detailed study of the teeth of these two groups suggests that they have evolved independently, and ''Yalkaparidon'' is anatomically otherwise very different from the marsupial moles. The incisors resemble those of diprotodontians, but no other features convincingly support this relationship, and the
convergent evolution of such incisors in South American 'pseudodiprotodont' groups (such as
caenolestids and polydolopimorphians) suggests that ''Yalkaparidon'' and diprotodontians may have evolved similar incisors independently. Basicranial similarities to bandicoots most likely represent shared plesiomorphic characters, and hence are not indicative of a close relationship.
For these reasons, ''Yalkaparidon'' is currently placed in its own
family, Yalkaparidontidae, and
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
, Yalkaparidontia; this placement would make this the only order of Australian marsupials known to have gone extinct. However, Frederick Szalay suggested in his 1994 book 'Evolutionary History of the Marsupials and an Analysis of Osteological Characters' that ''Yalkaparidon'' is indeed a
diprotodontian (as evinced by its incisors), albeit one that retains a highly primitive basicranium.
The exact function of its unusual
dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolo ...
remains obscure, and suggestions that it may have fed on
worms (based on the similarities of its molars to those of worm-eating tenrecs),
caterpillar
Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).
As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...
s or
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s are tenuous. However, its source of food presumably had a hard outer covering (necessitating use of the large incisors) but relatively soft interior, as zalambdodont molars cannot crush food items. The possibility that it was a "mammalian woodpecker" similar to the
aye-aye and
striped possum has been raised.
Morphology
A detailed study on its morphology, including newly referred tarsal material published in 2014 found that it was likely a crown group marsupial, and probably an australidelphian, but its unusual morphology made its precise placement uncertain.
References
External links
Yalkaparidon coheni from the lost kingdoms.com
{{Taxonbar, from1=Q142875, from2=Q12902672, from3=Q19776311
Prehistoric marsupial genera
Oligocene mammals of Australia
Miocene mammals of Australia
Riversleigh fauna
Fossil taxa described in 1988