The mandible and dentition of the Early Cretaceous monotreme Teinolophos trusleri
Date
2016
Authors
Rich, Thomas H.
Hopson, James A.
Gill, Pamela G.
Trusler, Peter
Rogers-Davidson, Sally
Morton, Steve
Cifelli, Richard L.
Pickering, David
Kool, Lesley
Siu, Karen
Journal Title
Journal ISSN
Volume Title
Publisher
Taylor & Francis
Abstract
The monotreme Teinolophos trusleri Rich, Vickers-Rich, Constantine, Flannery, Kool & van Klaveren, 1999 from the Early Cretaceous of Australia
is redescribed and reinterpreted here in light of additional specimens of that species and compared with the exquisitely preserved Early Cretaceous
mammals from Liaoning Province, China. Together, this material indicates that although T. trusleri lacked a rod of postdentary bones contacting
the dentary, as occurs in non-mammalian cynodonts and basal mammaliaforms, it did not share the condition present in all living mammals, including
monotremes, of having the three auditory ossicles, which directly connect the tympanic membrane to the fenestra ovalis, being freely suspended
within the middle ear cavity. Rather, T. trusleri appears to have had an intermediate condition, present in some Early Cretaceous mammals from
Liaoning, in which the postdentary bones cum ear ossicles retained a connection to a persisting Meckel’s cartilage although not to the dentary.
Teinolophos thus indicates that the condition of freely suspended auditory ossicles was acquired independently in monotremes and therian mammals.
Much of the anterior region of the lower jaw of Teinolophos is now known, along with an isolated upper ultimate premolar. The previously
unknown anterior region of the jaw is elongated and delicate as in extant monotremes, but differs in having at least seven antemolar teeth, which
are separated by distinct diastemata. The dental formula of the lower jaw of Teinolophos trusleri as now known is i2 c1 p4 m5. Both the deep
lower jaw and the long-rooted upper premolar indicate that Teinolophos, unlike undoubted ornithorhynchids (including the extinct Obdurodon),
lacked a bill.
Description
Keywords
Monotremata, Teinolophos, TMME, Cretaceous, Australia, dentition, mandible
Citation
Collections
Source
Alcheringa: An Australasian Journal of Palaeontology
Type
Journal article
Book Title
Entity type
Access Statement
Open Access