DEFINITION OF SUPRASPECIFIC TAXA

Formal ancestry-based definitions (sensu Rowe and Gauthier 1992; de Queiroz and Gauthier 1990, 1994; Bryant 1996) are presented here for emended taxonomic concepts for Tapirus and Tapiridae. Definitions for Ceratomorpha and Tapiromorpha are modified from Froehlich (1999) and Holbrook (1999), and definitions for Tapiroidea from Holbrook (1999). All definitions refer to either a type species, species, or a particular specimen as specifiers. Figure 4 illustrates the phylogenetic framework for these names and their specifiers.

Tapirus Brünnich 1772. Redefined here as the clade stemming from the most recent common ancestor of Tapirus indicus Desmarest 1819, Tapirus bairdii (Gill 1865), Tapirus pinchaque Roulin 1829, and the type species, Tapirus terrestris (Linnaeus 1758).

This crown-group definition codifies the general view that all living tapiroids belong to Tapirus (e.g., Colbert and Schoch 1998; Hershkovitz 1954; Nowak 1999; Prothero and Schoch 1989a, 1989b; Simpson 1945; Ray and Sanders 1984; Wilson and Reeder 1993). Eisenberg et al.’s (1990) referral of T. indicus to the genus Acrocodia is not followed here.

Tapiridae Burnett 1830. Redefined here as the clade stemming from the most recent common ancestor of PU 10899 (the type of Protapirus validus Hatcher 1896, here referred to P. simplex Wortman and Earle 1893, following Albright 1998) and Tapirus terrestris (Linnaeus 1758).

This node-based definition reflects the general consideration of North American Protapirus as a basal tapirid (e.g., Scott 1941; Radinsky 1963; Schoch 1989b; Hooker, 1989 ). Because the status of North American species of Protapirus is unclear (see Albright 1998), the articulated cranium of PU 10899, rather than a particular species, is used as a specifier. PU 10899 is the first described Protapirus in the literature with the distinctive, deep nasoincisive incisure (Hatcher 1896). Note that Scott’s (1941, plate 79) illustration of this specimen is a reconstruction based in part upon SDSM 2829. Although PU 10899 is currently referred to P. simplex (a species considered to include P. validus; Albright 1998 ), it is potentially a junior subjective synonym of P. obliquidens Wortman and Earle 1893 (see Albright 1998 ). It is also possible that New and Old World Protapirus are not monophyletic (Colbert and Schoch 1998; Colbert 1993), requiring the removal of North American ‘Protapirus’ from Protapirus sensu stricto. This definition differs from Holbrook (1999, p. 345), who generally defined tapiromorph ‘families’, including Tapiridae, as stem-based groups comprising “the type genus and all genera which are more closely related to it than to any other type genus.”

Tapiroidea Burnett 1830. Redefined here as the clade consisting of Tapirus terrestris (Linnaeus 1758) and all organisms that share a more recent common ancestor with Tapirus terrestris than with Rhinoceros unicornis Linnaeus 1758 (definition modified from Colbert and Schoch 1998).

The redefinition of the traditional, paraphyletic Tapiroidea (e.g., see Radinsky 1963), relegates many Eocene perissodactyls formerly considered tapiroids (e.g., Homogalax, Cardiolophus, Isectolophus, and apparently the Asian lophialetids, breviodontids, and rhodopagids) to the more inclusive Tapiromorpha ( Hooker 1984, 1989; Schoch 1989b; Dashzeveg and Hooker 1997; Colbert and Schoch 1998; Holbrook 1999). Although Heptodon is generally considered the most basally diverging tapiroid (see Dashzeveg and Hooker 1997;), it has also been hypothesized to fall outside this clade (e.g., Hooker, 1989 ). This definition is in keeping with Dashzeveg and Hooker (1997); consideration of the Tapiroidea as the group “comprising the extant family Tapiridae plus its more immediate extinct relatives,” and refines the similar stem-based definition of Holbrook (1999).

Ceratomorpha Wood 1937. Redefined here as the clade stemming from the most recent common ancestor of Rhinoceros unicornis Linnaeus 1758, and Tapirus terrestris (Linnaeus 1758). This reformulates Holbrook’s (1999) Ceratomorpha by explicitly identifying specifying species.

Tapiromorpha Haeckel 1873. Redefined here as the clade consisting of Tapirus terrestris Linnaeus 1758 and all organisms that share a more recent common ancestor with Tapirus terrestris than with Equus caballus Linnaeus 1758.

This stem-based definition uses specifying species to refine Froehlich’s (1999) and Holbrook’s (1999) definitions of Tapiromorpha. Although Tapiromorpha has been applied to several different taxonomic assemblages in the past (see Schoch 1989a ), it is commonly considered to be the sister-taxon to Hippomorpha.