Tianyulong

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Tianyulong
Temporal range:
Ma
↓
Specimen IVPP V17090, muzzle, hand, feet and tail framed in red
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: †Ornithischia
Family: †Heterodontosauridae
Genus: †Tianyulong
Zheng et al., 2009
Species:
†T. confuciusi
Binomial name
†Tianyulong confuciusi
Zheng et al., 2009

Tianyulong (

Liaoning Province, China.[1]

History

The

Jehol group. The fossil was collected at a locality transliterated as Linglengta or Linglongta. Lu et al., 2010, reported that these beds were actually part of the Tiaojishan Formation, dating from the late Jurassic period at least 158.5 million years ago.[2]

Another specimen, IVPP V17090, was described in 2012. At least four other specimens remain undescribed.[3]

Description

Heterodontosaurus tucki. However, Tianyulong had unusual proportions compared to other heterodontosaurids. The head was large and the legs and tail were long, but the neck and forelimbs were short.[3]

Tianyulong has a row of long, filamentous

feathers and raises the possibility that the earliest dinosaurs and their ancestors were covered with homologous dermal
filamentous structures that can be considered primitive feathers ("proto-feathers").

Classification

Skull diagrams of Heterodontosaurus and Tianyulong

Tianyulong is classified as a heterodontosaurid, a group of small ornithischian dinosaur characterized by a slender body, long tail and a pair of enlarged canine-like tusks. They were herbivorous or possibly omnivorous. Until the discovery of Tianyulong, known members of the group were restricted to the Early Jurassic of South Africa, with one genus (Fruitadens) from the Late Jurassic of the US, and possibly one additional genus (Echinodon) from the Early Cretaceous of England.

The cladogram below follows the analysis by Butler et al., 2011:[4]

Heterodontosauridae 

Paleobiology

Restoration

The filamentous integumentary structures are preserved on three areas of the fossil: in one patch just below the neck, another one on the back, and the largest one above the tail. The hollow filaments are parallel to each other and are singular with no evidence of branching. They also appear to be relatively rigid, making them more analogous to the integumentary structures found on the tail of

theropods. Among the theropods, the structures in Tianyulong are most similar to the singular unbranched proto-feathers of Sinosauropteryx[6] and Beipiaosaurus.[7] The estimated length of the integumentary structures on the tail is about 60 mm which is seven times the height of a caudal vertebra. Their length and hollow nature argue against of them being subdermal structures such as collagen
fibers. Such dermal structures have previously been reported only in derived theropods and ornithischians, and their discovery in Tianyulong extends the existence of such structures further down in the
pterosaurs. The authors (in supplementary information to their primary article) noted that discovery of similar filamentous structures in the theropod Beipiaosaurus bolstered the idea that the structures on Tianyulong are homologous with feathers. Both the filaments of Tianyulong and the filaments of Beipiaosaurus were long, singular, and unbranched. In Beipiaosaurus, however, the filaments were flattened. In Tianyulong, the filaments were round in cross section, and therefore closer in structure to the earliest forms of feathers predicted by developmental models.[1] A study published in the journal Biology Letters rigorously tested the hypothesis that protofeathers are plesiomorphic to dinosaurs. The results supported the hypothesis that scales are plesiomorphic to dinosaurs.[8] While it is true that feather beta keratin is present in crocodilian scales in embryonic development,[9] it fails to support the maximum-likelihood of protofeathers being plesiomorphic.[8]

References

  1. ^
    S2CID 4423110
    .
  2. ^ Liu Y.-Q. Kuang H.-W., Jiang X.-J., Peng N., Xu H. & Sun H.-Y. (2012). "Timing of the earliest known feathered dinosaurs and transitional pterosaurs older than the Jehol Biota." Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication).
  3. ^
    PMID 23166462
    .
  4. doi:10.1111/j.1475-4983.2011.01046.x.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  5. S2CID 17781405
    .
  6. doi:10.1139/cjes-38-12-1705
    .
  7. PMID 19139401
    .
  8. ^
    PMID 26041865
    .
  9. PMID 23744807
    .

External links
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