Nipponoolithus

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Nipponoolithus
Temporal range: Albian
Egg fossil classification Edit this classification
Oofamily: incertae sedis
Oogenus: †Nipponoolithus
Tanaka et al. 2016
Oospecies
  • †N. ramosus Tanaka et al. (2020)
  • †N. rumosus Tanaka et al. (2016) (type)

Nipponoolithus is an

maniraptor.[1]

Distribution

Nipponoolithus remains are known from the

Tamba, Hyogo, Japan. The site is dated to the lower Albian.[1]

History

Though fossil dinosaur skeletons are rare in Japan, they have been well-documented since 1978.[1] The first Japanese fossil eggs were discovered in 2003: Yoichi Azuma documented numerous eggs of the Ratite morphotype in the Kitadani Formation,[2] and Ren Hirayama et al. documented dinosaur and turtle eggshells in the Kuwijima Formation.[3] However, these eggs were never described in detail.[1] In 2006, the dinosaur-rich Kamitaki locality in the Sasayam Group was discovered. In 2016, a team of paleontologists from Japan and Canada collected numerous fossilized eggs at Kamitaki, including the specimens which they would refer to a new oogenus and oospecies: Nipponoolithus rumosus.[1]

Description

Nipponoolithus rumosus is known only from a handful of isolated eggshell fragments ranging from 0.36 to 0.53 mm in thickness, just barely larger than a chicken egg.[1][4] It is estimated, based on the eggshell thickness, that Nipponoolithus eggs weighed about 100 grams (3.5 oz), making it among the smallest fossil dinosaur eggs ever discovered.[1]

Like most non-

dinosaur eggs, it has two layers:[5] the outer continuous layer, and the inner mammillary layer.[1] The continuous layer is two to four times thicker than the mammillary layer. Nipponoolithus's outer surface is ornamented with low, branched ridges, similar to ornamentation observed in Macroelongatoolithus, Montanoolithus, Paraelongatoolithus, Reticuloolithus, Spheruprismatoolithus, and the eggs of Deinonychus.[1] The crystals in the mammillary layer are acicular or wedge-like.[1]

Paleobiology

N. rumosus was most likely laid by some kind of non-

Jehol biota in China.[1]

Parataxonomy

Nipponoolithus has not been place into any described oofamily. It contains a single oospecies: N. rumosus.[1]

References

  1. ^ a b c d e f g h i j k l Tanaka, K., Zelenitsky, D. K., Saegusa, H., Ikeda, T., DeBuhr, C. L., & Therrien, F. (2016). Dinosaur eggshell assemblage from Japan reveals unknown diversity of small theropods. Cretaceous Research, 57, 350–363.
  2. ^ Azuma, Y. (2003). "Early Cretaceous vertebrate remains from Katsuyama city, Fukui Prefecture, Japan." Memoir of the Fukui Prefectural Dinosaur Museum, 2: 17–21
  3. ^ Hirayama, R., Manabe, M., Isaji, S., Barrett, P.M., Evans, S.E., Yabumoto, Y., Matsuoka, H., Yamaguchi, I., Yamaguchi, M., (2003) "Vertebrate fauna from the Early Cretaceous Kuwajima Formation of Shiramine Village, Ishikawa Prefecture, central Japan." Memoir of the Fukui Prefectural Dinosaur Museum, 2: 15–16
  4. ^ Miller, KK (2015). "World’s smallest dinosaur egg just discovered in Hyogo Prefecture" Rocket News 24.
  5. ^ Laura E. Wilson, Karen Chin, Frankie D. Jackson, and Emily S. Bray. II. Eggshell morphology and structure. UCMP Online Exhibits: Fossil Eggshell
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