March 3, 2015
Fishy Friday #7
1. A. The fossil look likes a lizard
B. Here is the list of bones founded on the fossils:
C. I can tell it is dorsal view since the vertical direction is pertaining to or toward the back plane of the body. The skeleton of the Liaocondon hui is near the upper surface.
2. Sulcus: a groove or furrow, especially one on the surface of the brain
OMC: Ossified Mandibular Cartilage begins at the end of embryonic period and is completed in the fetal period and the portion that participates in mandibular formation is determined.
Ectotympanic: a bony ring that holds the eardrum or tympanic membrane. Its position and attachment to the skull vary within mammals, and particularly in primates, and can be intrabullar or extrabullar.
3. The main question addressed in this study is that eardrum was stabilized with the ossified cartilage as a supporting structure. OMC serves as a stabilizing mechanism bridging the dentary and the detached ossicles during mammalian evolution.
4. A. The scientific name for this fossil mammal is Licaocondon Hui.
B. Liao was named in part for the bountiful fossil beds in Liaoning, China, where it was found. Condon is latin word for ‘cuspate tooth’, a common suffix for generic name in ‘tricondontts’. The species name, Hui honors paleontologist Yaoming Hu, a student dedicated to study of Mesozoic animals.
C. It is 122-125 million years old. It is a medial-sized eutriconodont with a body length of 195 mm from the tip of the rostrum to the hip or 357 mm from the tip of the rostrum to the tail (35.7 cm).
5. The TMME can be characterized by several features: the articular, prearticular and angular lose their direct contact with the dentary and are supported anteriorly by Meckel’s cartilage, in adult; the malleo-incudal articulation lost its primary function for jaw suspension; all ear ossicles are primarily auditory structures but are not completely free from the feeding apparatus; the tympanic membrane is not fully suspended by the ectotympanic, and the manubrium of the malleus has not developed. The DMME is defined by the loss of embryonic Meckel’s cartilage and disconnection of the middle ear from the mandible in adults. It is a major feature distinguishing living mammals from nonmammlian vertebrate.
The definitive mammalian middle ear is completely separated from the jaw, while the transitional mammalian middle ear is still supported by a jaw-associated bone. The mandibular middle ear is regarded as the prototype that gives rise to the DMME in which the angular, articular plus prearticular, and quadrate are stricitly auditory structures and fully divorced from the feed apparatus.
6. A. For parts h and i, it shows the medial and lateral views of the ossicles of Opossum. For parts f and g, it shows the dorsal and ventral views of the ossicles of Platypus.
B. These ears are similar to the new fossil by having the similar features associated with bones and the groove on the lower jaw, which indicated the presence of ossified Meckel’s cartilage.
7. The Liaoconodon hui is being compared to the basal, early mammaliaforms like Morganucodon, because it shows the relationship where the middle ear bones are part of the mandible and the definitive middle ear of living and fossil mammals.
8. A. The platypuses are more closely related to eutricondonts because they both shared common ancestor. They both shared the similar dental and mandibular characteristic. An anatomical feature (meckelian groove present) of MME is present within both platypuses and eutriconodonts; this suggested that the…