Giant Hutias (Heptaxodontidae)

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Giant hutias

(Heptaxodontidae)

Class Mammalia

Order Rodentia

Suborder Hystricognathi

Family Heptaxodontidae

Thumbnail description
Very large island rodents with distinctively shaped molars

Size
31–440 lb (14–200 kg)

Number of genera, species
4 genera, 5 species

Habitat
Lowland and montane tropical rainforest

Conservation status
All species are presumed extinct

Distribution
Several islands of the Greater and Lesser Antilles

Evolution and systematics

The native rodents of the West Indies, living and extinct, are an extraordinarily diverse group. They are sorted by taxonomists into four families, 15 genera, and about 60 species, including family Heptaxodontidae, with four genera and five species.

Only Pleistocene and Recent (post-Pleistocene to present) fossils and subfossils are known for the Heptaxodontidae, most of these recovered from caves. The Heptaxodontidae most likely arose in isolation on the islands of the Antilles from an ancestral species that rafted from the mainlands of the Americas. Taxonomists have tried to link the family with the families Myocastoridae (nutria), Chinchillidae (chinchillas and viscachas), Capromyidae (hutias), and Dinomyidae (pacaranas and related species).

At least one genus, Quemisia, may still have been extant when Native Americans first occupied the islands, in 7000 b.c., while Clidomys and Amblyrhiza apparently became extinct during the Pleistocene Epoch before the arrival of humans on the Antilles.

Physical characteristics

The skulls of heptaxodontids are massive, resembling those of the nutria (Myocastoridae). The rostrum (snout) was massive, the bullae (bones of the inner ear) were small, and many of the skulls bear sagittal crests (bony ridges on the top of the skull to provide added anchorage for strong jaw mucles).

The cheek teeth, or molars, were strongly hypsodont ("high-crowned"), each having four to seven laminae (layers), set more or less parallel while arranged at angles to the long axis of the skull. Quemisia and Elasmodontomys had teeth and jaw adaptations for propalinal (side-to-side) chewing.

The skulls and postcranial bones suggest that the Hepataxodontidae had heavy-set bodies. All species were considerably larger than the general run of rodents today. Amblyrhiza was nearly the size of a black bear (Ursus americanus).

Distribution

Amblyrhiza inhabited the islands of Anguilla and St. Maarten when both islands were part of a much larger, dry landmass now called the Anguillan Bank. Quemisia lived on Hispaniola, Elasmodontomys in Puerto Rico, and Clidomys in Jamaica.

Habitat

Probably lowland and montane tropical rainforest.

Behavior

Nothing is known.

Feeding ecology and diet

Unknown. Most likely predominantly or completely herbivorous.

Reproductive biology

Nothing is known. Mammals in the size range of the Heptaxodontidae, on islands with limited areas and resources, would have tended toward smaller litters.

Conservation status

All heptaxodontid species are considered extinct. The presence of remains of some species among human refuse and artifacts suggests that they were hunted as food by Native Americans, who began settling the Antilles in 7000 b.c.Clidomys and Amblyrhiza probably became extinct long before the Native American colonization.

Some living heptaxodontids were probably present when the first Europeans began settling the West Indies in a.d.1500. Early Spanish explorers briefly described an animal slightly larger than a hutia (Capromyidae) that was a source of food for the aboriginals, who called the creature "quemi," and which may have been a heptaxodontid.

Significance to humans

Some species used as food source for Native Americans. The remains of Heptaxodontidae allow valuable scientific insight into the dynamics of adaptive evolution on islands.

Common name / Scientific name/Other common names	Physical characteristics	Habitat and behavior	Distribution	Diet	Conservation status
Anguilla-St. Martin giant hutia Amblyrhiza inundata	Some individuals reached the size of an American black bear (Ursus americanus). Adult sizes vary from a low of about 110 lb (50 kg) to a high of about 440 lb (200 kg). The distinctive, obliquely orientated laminae on the molars average out at 35° from the long axis of the skull.	Probably lived in tropical rainforest. Behavior is unknown.	Remains have been found on the islands of Anguilla and St. Martin in the northern Lesser Antilles.	Unknown, but presumably herbivorous.	Extinct
Hispaniolan giant hutia Quemisia gravis	Weight about 31 lb (14 kg), about the same size as Elasmodontomys. It had an unusual twisting of the enamel pattern of the molars. The obliquely orientated laminae on the molars average out at 55° from the long axis of the skull.	Probably tropical rainforest. Behavior is unknown.	Hispaniola. The species is known only from bones found in caves near St. Michel in Haiti and Samana Bay in the Dominican Republic.	Unknown, but presumably herbivorous.	Extinct
Puerto Rican giant hutia Elasmodontomys obliquus	A large, terrestrial rodent with a heavy-set body and a body weight of 31 lb (14 kg). The flat-topped skull resembles that of a nutria (Myocastor coypus). The short bones of its digits indicate that it was terrestrial and not arboreal. The obliquely orientated laminae on the molars average out at 45° from the long axis of the skull.	Probably lowland and montane tropical rainforest. Behavior is unknown.	The species is known only from bones recovered from cave deposits in Puerto Rico.	Unknown, but presumably herbivorous.	Extinct

Resources

Books

Woods, Charles A., ed. Biogeography of the West Indies: Past, Present, and Future. Gainesville, FL: Sandhill Crane Press, 1989.

Periodicals

Biknevicius A., D. A. McFarlane, and R. D. E. MacPhee. "Body size in Amblyrhiza inundata (Rodentia; Caviomorpha) an extinct megafaunal rodent from the Anguilla Bank, West Indies: estimates and implications." American Museum Novitates 3079 (1993): 1–25.

Burness, G., J. Diamond, and T. Flannery. "Dinosaurs, dragons, and dwarfs: The Evolution of Maximal Body Size." Proceedings of the National Academy of Sciences, USA 98(2001): 14518–14523.

Buskirk, R. E. "Zoogeographic Patterns and Tectonic History of Jamaica and the Northern Caribbean." Journal of Biogeography 12 (1985): 445–461.

Huyghe, P. "A Brobdingnagian Rodent (Giant Rodent Amblyrhiza Inundata)." Omni (March 1, 1994).

MacPhee, R. D. E. "Quaternary Mammal Localities and Heptaxodontid Rodents of Jamaica." American Museum Novitates 2803 (1984): 1–34.

McFarlane, D. A., R. D. E. MacPhee, and D. Ford. "Body Size Variability and a Sangamonian Extinction Model for Amblyrhiza, a West Indian Megafaunal Rodent." Quaternary Research 50 (1998): 80–89.

Morgan, G. S., and C. A. Woods. "Extinction and Zoogeography of West Indian Land Mammals." Biological Journal of the Linnean Society 28 (1986): 167–203.