''Astrochelys rogerbouri'' is an extinct

tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like ot ...

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

in the family Testudinidae which formerly lived in

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

Discovery and naming

The type specimen, MNHN.F.MAD480, is a nearly complete

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

and was collected in June 1900 in Ambolisatra,

Guillaume Grandidier Guillaume Grandidier (1 July 1873 – 13 September 1957) was a French geographer, ethnologist, zoologist who studied the island of Madagascar. He was the son of the wealthy industrialist Alfred Grandidier also a zoologist and expert on Madagascar. ...

. It is kept at the

Muséum national d’histoire naturelle The French National Museum of Natural History, known in French as the ' (abbreviation MNHN), is the national natural history museum of France and a ' of higher education part of Sorbonne Universities. The main museum, with four galleries, is loca ...

. This material was originally assigned as a juvenile specimen of '' Aldabrachelys abrupta'', likely as the two share a type locality, and it was only found to represent a new species after DNA analysis. The specific name honors Roger Bour, a

herpetologist Herpetology (from Greek ἑρπετόν ''herpetón'', meaning " reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians (gymnophiona)) and r ...

and expert on western Indian Ocean giant tortoises who helped in the investigation describing this species.

Description

''Astrochelys rogerbouri'' was a large tortoise species, with an estimated straight

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the und ...

length of 50 cm. This matches the size of its

congeneric Congener may refer to: * A thing or person of the same kind as another, or of the same group. * Congener (biology), organisms within the same genus. * Congener (chemistry), related chemicals, e.g., elements in the same group of the periodic table. ...

relative, the

angonoka tortoise The angonoka tortoise (''Astrochelys yniphora'') is a critically endangered species of tortoise severely threatened by poaching for the illegal pet trade. It is endemic to Madagascar. It is also known as the angonoka, ploughshare tortoise, M ...

, which has a maximum straight carapace length of 51.9 cm. Though it is only known from a tibia, its

mitochondrial genome Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

shows deep

genetic divergence Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time, often leading to reproductive isolation and continued mutation even after the populations hav ...

, supporting its status as a distinct species.

Ecology

In Ambolisatra, the presence of both ''A. rogerbouri'' and '' Aldabrachelys abrupta'' have been confirmed through genomic analysis of remains found at the site, confirming that the two species occurred in microsympatry. Additional remains from Ambolisatra have been morphologically referred to ''

Aldabrachelys grandidieri ''Aldabrachelys grandidieri'', or Grandidier's giant tortoise, is an extinct species of tortoise that was endemic to Madagascar. Mitochondrial DNA extracted from subfossil bone confirm that it is a distinct species. Description ''Aldabrache ...

'' and the extant radiated tortoise (''

Astrochelys radiata The radiated tortoise (''Astrochelys radiata'') is a tortoise species in the family Testudinidae. Although this species is native to and most abundant in southern Madagascar, it can also be found in the rest of this island, and has been in ...

''), but these records have not been genetically verified. The subfossil bones found in Ambolisatra assigned to ''Astrochelys radiata'' (as well as 3 other subfossil records of ''A. radiata'' and ''Astrochelys'' sp. outside the current range of the species) may represent ''Astrochelys rogerbouri''. Though the remains identified as ''Aldabrachelys grandidieri'' from Ambolisatra are fragmentary and their assignment is questionable, Ambolisatra is geographically within the range of genetically-confirmed ''Aldabrachelys grandidieri'' records, and the species may indeed have coexisted with ''Astrochelys rogerbouri'' there. Ambolisatra is also near the northwestern limit of the radiated tortoise's current range, and within the range of the extant

spider tortoise The spider tortoise (''Pyxis arachnoides'') is a species of tortoise in the family Testudinidae that is endemic to Madagascar and is one of only two species in the genus ''Pyxis''. Habitat The remaining tortoises are found only in south western ...

(''Pyxis arachnoides''). In total, 5 tortoise species undoubtedly formerly lived in southwestern Madagascar (the spider tortoise, the two extinct ''Aldabrachelys'' species, the radiated tortoise and ''Astrochelys rogerbouri''), an exceptional level of

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species s ...

tortoise diversity. Judging from the former sympatry of ''A. rogerbouri'' and the

radiated tortoise The radiated tortoise (''Astrochelys radiata'') is a tortoise species in the family Testudinidae. Although this species is native to and most abundant in southern Madagascar, it can also be found in the rest of this island, and has been intro ...

, the two may have had different preferences in diet or habitat, and the

may be hypothesized to have shared such preferences with ''A. rogerbouri''.

Extinction

It is unknown when ''A. rogerbouri'' became extinct, though it is believed to have survived until 1262 to 1069 years B.P. at least.

References

External links

{{Taxonbar, from=Q116765606 Astrochelys Extinct animals of Madagascar Holocene extinctions Fossil taxa described in 2023 Extinct turtles