Incisor enamel microstructure of West Indian caviomorph hystricognathous rodents (Octodontoidea and Chinchilloidea)

Analysis of the incisor enamel microstructure extinct and extant West Indian caviomorph rodents emphasizes a clear microstructural distinction between Echimyidae (Capromyinae Heteropsomyinae) among Octodontoidea “Heptaxodontidae”, whose phylogenetic affinities are debated. All capromyines heteropsomyines have pattern characterized by rectangular crystallite arrangement, which is biomechanically strongest in limiting crack propagation most efficiently (subtype [Sbt.] 3 multiserial Hunter-Schreger bands [HSBs]). This condition exclusive to all mainland octodontoids. In stark contrast, “heptaxodontids” sampled here exhibit much less derived subtypes HSBs, with parallel acute angular arrangement (Sbt. 1 [Clidomys], Sbt. 1–2 [Elasmodontomys], low 2 [Amblyrhiza]), well adapted for prevention propagation. The Amblyrhiza Clidomys consistent chinchilloid assignment, as reflected anatomy their auditory region unusual dental pattern. For Elasmodontomys, primitive its difficult reconcile highly nested position within clade (among Capromyinae), recently inferred from aDNA analyses. different patterns caviomorphs indicate distinct high-level taxonomic groups, but restricted Octochinchilloi (Octodontoidea Chinchilloidea) Caviomorpha. great diversity on Caribbean islands resulted intra-archipelago diversification through time, can only be explained sources, implying de facto multiple (potentially time-staggered) natural colonizations Indies. chinchilloid-compatible characterizing Borikenomys lower Oligocene deposits Puerto Rico strongly suggest link some recently-extinct “heptaxodontids”, would substantiate greater antiquity islands.