Rapetosaurus

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Rapetosaurus
Temporal range:
Ma
↓
Juvenile skeleton, Field Museum of Natural History
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: †Sauropodomorpha
Clade: †Sauropoda
Clade: †Macronaria
Clade: †Titanosauria
Clade: †Lithostrotia
Genus: †Rapetosaurus
Curry Rogers & Forster, 2001
Species:
†R. krausei
Binomial name
†Rapetosaurus krausei
Curry Rogers & Forster, 2001

Rapetosaurus (

Period. Only one species
, Rapetosaurus krausei, has been identified.

Like other sauropods, Rapetosaurus was a quadrupedal herbivore; it is calculated to have reached lengths of 15 metres (49 ft).

Description

Rapetosaurus restoration

Rapetosaurus was a fairly typical sauropod, with a short and slender

diplodocid, with a long, narrow snout and nostrils on the top of its skull
. It was a herbivore and its small, pencil-like teeth were good for ripping the leaves off trees but not for chewing.

It was fairly modest in size, for a

titanosaur. The juvenile specimen measured 8 metres (26 ft) from head to tail, and "probably weighed about as much as an elephant". An adult would have been about twice as long (15 metres (49 ft) in length)[2] which is still less than half the length of its gigantic kin, like Argentinosaurus and Paralititan. In 2020 Molina-Perez and Larramendi estimated the size of the probable adult specimen (MAD 93-18), which is known from a femur, at 16.5 meters (54 ft) and 10.3 tonnes (11.35 short tons).[3]

Discovery and naming

Skull cast, Royal Ontario Museum, Canada.

The discovery of Rapetosaurus, known by the single species Rapetosaurus krausei marked the first time a

titanosaurs that are known only from partial fossilized
remains.

The discovery was published in 2001 by Kristina Curry Rogers and Catherine A. Forster in the scientific journal Nature. The nearly-complete skeleton is that of a juvenile and partial remains from three other individuals were also recovered.

Skeletal reconstruction of R. krausei, scaled as juvenile specimen FMNH PR 2209.

The dig uncovered a partial skull (UA 8698, the holotype specimen), another partial skull, a juvenile skeleton missing only a few tail vertebrae, and an unrelated vertebra. The juvenile skeleton, in particular, is the most complete titanosaur skeleton ever recovered and the only one with a head still attached to the body.

The fossilized remains were found in the Mahajanga basin in northwest

Universite d'Antananarivo
. The team leader, David Krause, had been excavating fossils from the site since 1993.

The generic name Rapetosaurus is derived from Rapeto (a

Malagasy folklore credited for the geographical features of the land[4]) and sauros, which is Greek for lizard. The species epithet, krausei, is named after the team leader of the expedition, David W. Krause
.

Paleobiology

Growth

Field Museum mount in side view

A rare specimen of a juvenile Rapetosaurus was uncovered in a museum collection by Kristina Curry Rogers and colleagues. The specimen was estimated to weigh about 40 kilograms (88 pounds) and was likely between 39 and 77 days old by the time of its death. At the time of its hatching, the juvenile Rapetosaurus was estimated to be 3.4 kilograms (7.8 pounds) in weight. Based on bone remodeling, the juvenile sauropod was also believed to have been capable of surviving with little to no parental care. Analysis of the bones further revealed the young Rapetosaurus likely starved to death due to Cretaceous Madagascar's harsh droughts.[5][6]

Paleoecology

Mounted Majungasaurus and Rapetosaurus

During the Maastrichtian, like it is now, Madagascar was an island, having

marine environment.[7]

Besides Rapetosaurus, fossil taxa recovered from the Maevarano include

eutherians, the former reaching large sizes such as Vintana
.

Restoration of two Majungasaurus chasing Rapetosaurus

The skull of

theropod, was discovered in 1996. It is similar to species found in India and Argentina, indicating that land bridges between the fragments of the former supercontinent of Gondwana still existed in the late Cretaceous, far later than was previously believed. The most likely occurrence was a land bridge allowing animals to cross from South America to Antarctica, and then up to India and Madagascar. Majungasaurus was the largest predator in its environment, while the only known contemporaneous large herbivores were sauropods like Rapetosaurus. Scientists have suggested that Majungasaurus specialized in hunting sauropods. Majungasaurus tooth marks on Rapetosaurus bones indicate that it at least fed on these sauropods, whether or not it actually killed them.[15]

Typically, titanosaurs were unusual among sauropods in that they coexisted with large

ankylosaurs. However, Rapetosaurus was atypical among titanosaurs in that it shared the Mahajanga basin with only one other large herbivore, another titanosaur. Smaller herbivores were rare, with only one, Simosuchus, being discovered during over 100 years of collection in that area. Due to the absence of ornithischian dinosaurs, it is suggested that prehistoric Madagascar saw a different herbivore community dynamic than was seen elsewhere in the Cretaceous.[1]

References

  1. ^
    S2CID 4347583
    .
  2. JSTOR 24321451
    .
  3. Bibcode:2020dffs.book.....M
    .
  4. ^ Zoë Crossland, Ancestral Encounters in Highland Madagascar: Material Signs and Traces of the Dead, Cambridge University Press, 17/02/2014
  5. ^ "Rapetosaurus krausei: Tiny titanosaurus was just a few weeks old, scientists say - Los Angeles Times". Los Angeles Times. 21 April 2016.
  6. ^ "Lap Dinos? Gigantic Sauropods Started Out Chihuahua-Size | Live Science". Live Science. 21 April 2016.
  7. ^
    S2CID 130262308. {{cite book}}: |journal= ignored (help
    )
  8. doi:10.1130/G21036.1
    .
  9. ^
    S2CID 9166607
    .
  10. S2CID 4364184
    .
  11. PMID 9506938
    .
  12. S2CID 27078534
    .
  13. S2CID 205013285
    .
  14. S2CID 13274054. {{cite book}}: |journal= ignored (help
    )
  15. S2CID 4389583
    .

Sources

External links

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