Echimyidae is the family
Characteristics
In general form, most spiny rats resemble
, although they are more closely related to
and
. Most species have stiff, pointed hairs, or spines, that presumably serve for protection from predators.
Many echimyids can Autotomy when attacked. This action may confuse long enough for the spiny rat to escape. Unlike the tails of some species of , however, the tails of spiny rats do not regenerate. Therefore, the tactic can only be used once in an individual's lifetime.
Most spiny rats are rare and poorly known, but a few are extremely abundant. Various species are respectively terrestrial, arboreal, or fossorial. In general, the arboreal forms are most rat-like in appearance, whilst the burrowing species are more gopher-like, with stocky bodies and short tails. Most species do poorly in conditions of high heat and and are restricted to regions with abundant water. They are almost exclusively herbivore.
Systematics
The current taxonomic content of the family Echimyidae has been reshaped over time, and its organization into coherent units stems from two realizations. The first is that
cladistic approaches applied to morphological characters showed that many traits used to define taxa were
plesiomorphic or
homoplastic. The second realization came from the advent of
phylogenetic analyses of
DNA sequence and
protein sequence data with probability methods — maximum likelihood and Bayesian inference — leading to the identification of robust
clades and the recognition of higher categorical ranks (see Phylogeny section).
The following table recapitulates and compares the taxonomic content of taxa recognized on molecular and traditional basis: the two families
Capromyidae and
Myocastoridae, the five subfamilies
Echimyinae, Euryzygomatomyinae,
Capromyinae,
Dactylomyinae,
Eumysopinae, and the four tribes
Echimyini,
Myocastorini,
Capromyini, and
Plagiodontini.
Extant genera
-
Family Echimyidae - spiny rats
+ Comparison between molecular-based
for extant Echimyidae and Capromyidae genera
! style="width: 12em;" | Genus
! style="width: 12em;" | Vernacular name
! style="width: 12em;" | Molecular-based subfamily
! style="width: 12em;" | Molecular-based tribe
! style="width: 12em;" | Traditional systematics |
| Echimyinae |
| Atlantic tree-rats |
| — |
| — |
| giant tree-rat |
| — |
| red-crested tree-rat |
| toros or brush-tailed rats |
| Dactylomyinae |
| olalla rats |
| Atlantic bamboo rat |
| Eumysopinae |
| spiny tree-rats |
| Echimyinae |
| Myocastoridae |
| Eumysopinae |
| armored rat |
| spiny rats |
| — |
| guiara |
| — |
| Carterodontinae |
| Capromyidae |
| Capromyini |
| Mesocapromys |
| Mysateles |
| Desmarest's hutia |
Extinct genera
-
Family Echimyidae - spiny rats
About Chaetomys
The bristle-spined rat,
Chaetomys subspinosus, has sometimes been classified in Echimyidae,
although traditionally considered a member of the New World porcupine family
Erethizontidae.
The classification with Echimyidae is supported by similarities in the
premolar structure.
Like all living caviomorphs except erethizontids,
Chaetomys seems to lack posterior carotid foramina, and together with all echimyids and in contrast to all other caviomorphs,
Chaetomys seems to retain the otherwise deciduous premolars (dP4).
Some of these characters have been, however, reinterpreted as evidence for affinities between
Chaetomys and the Erethizontidae.
A molecular
phylogeny based on the
mitochondrial gene coding for
cytochrome b combined to
karyology evidence actually suggests
Chaetomys is more closely related to the Erethizontidae than to the Echimyidae, although it branches as the sister group to the rest of the Erethizontidae.
Phylogeny
The phylogenetic tree of the Echimyidae shows a major split between the subfamily
Echimyinae and an assemblage containing the Euryzygomatomyinae,
Carterodon, and the
Capromyidae.
The first major clade contains a majority of arboreal genera (e.g.,
Phyllomys,
Dactylomys, and
Mesomys), a few terrestrial taxa (e.g.,
Proechimys), and a subaquatic one (
Myocastor).
The second major clade includes fossorial genera (e.g.,
Euryzygomatomys or
Carterodon), a terrestrial one (
Trinomys), and members inhabiting the Caribbean islands (Capromyidae).
References and notes
