Registration Number: 51
Definition: The largest crown clade contain- ing Iguana (Lacerta) iguana (Linnaeus 1758) (Iguanidae), Agama (Lacerta) agama (Linnaeus 1758) (Agamidae), and Chamaeleo (Lacerta) chamaeleon (Linnaeus 1758) (Chamaeleonidae), but not Lacerta agilis Linnaeus 1758 (Lacertidae) and Scincus (Lacerta) scincus (Linnaeus 1758) (Scincidae) and Anguis fragilis Linnaeus 1758 (Anguidae) and Coluber constrictor Linnaeus 1758 (Serpentes). This is a maximum-crown- clade definition. Abbreviated definition: max crown ▿ (Iguana iguana (Linnaeus 1758) &
Agama agama (Linnaeus 1758) & Chamaeleo chamaeleon (Linnaeus 1758) ~ Lacerta agi- lis Linnaeus 1758 & Scincus scincus (Linnaeus 1758) & Anguis fragilis Linnaeus 1758 &
Coluber constrictor Linnaeus 1758).
Etymology: Derived from Iguana, the name of one of its subclades, which is based on the Spanish “Iguana”, which is in turn derived from the Carib “iwana” (Burghardt and Rand, 1982).
Reference Phylogeny: The primary reference phylogeny is Figure 6 of Estes et al. (1988).
Composition: Iguania is composed of two pri- mary crown clades, Iguanidae (Pleurodonta of some authors) and Acrodonta (Macey et al., 1997;
Schulte et al., 2003; Gauthier et al., 2012), the lat- ter composed of Agamidae and Chamaeleonidae, and approximately 1,876 currently recognized extant species (Uetz, 2017). Estes (1983) pre- sented a compilation of the lizard fossil record including Iguania, and subsequent additions can
be found in Evans (2003), Conrad and Norell (2007), Conrad (2008, 2015), Longrich et al.
(2012), Smith and Gauthier (2013), Simões et al. (2015), Apesteguía et al. (2016), and possibly DeMar et al. (2017).
Diagnostic Apomorphies: Estes et al. (1988) listed 14 apomorphies of Iguania, including the following:
1. Frontals fuse embryonically (Estes et al., 1988).
2. Frontals strongly constricted between orbits (Estes et al., 1988).
3. Broad frontal shelf underlying nasals (Estes et al., 1988).
4. Postfrontal reduced (or absent), not forked, and confined to orbital rim (Estes et al., 1988; Presch, 1988).
5. Parietal foramen on frontoparietal suture or within frontal (Estes et al., 1988).
6. M. intercostalis ventralis absent (Camp, 1923).
7. Tongue mucocytes mostly serous and sero-mucous (Gabe and Saint Girons, 1969; Schwenk, 1988).
Some of these characters exhibit reversals within Iguania (3,5) or independent (convergent or parallel) origin in other Squamata (1,2,5) and therefore are diagnostic only when used in com- bination with other characters. Gauthier et al.
(2012) identified additional iguanian apomor-
phies (40 total, 21 unambiguous) including a
novel kinetic joint between the postorbital and
squamosal bones (reversed in some Acrodonta).
Synonyms: Iguanomorpha sensu Sukhanov
(1961) corresponds in terms of composition but was not defined phylogenetically and is therefore an approximate synonym. The fol- lowing names are partial (and approximate) synonyms of Iguania in the paraphyletic sense that excludes chamaeleonids (see Comments), though some included taxa no longer con- sidered iguanians, such as Cordylus and even Pterodactylus: Iguaniens of Cuvier (1817, 1829), Duméril and Bibron (1834–1854), and Duméril and Duméril (1851); Crassilingues of Wiegmann (1834); Eunotes of Duméril and Bibron (1834–1854) and Duméril and Duméril (1851); Iguanii of Latreille (1825); Pachyglossae of Wagler (1828, 1830); Stellionidae of Bonaparte (1831); Crassilinguia of Gravenhorst (1843); Strobilosaura of Gray (1845); Iguanidae of Jones (1847–1849); Pachyglossa of Stannius (1856), Cope (1900), and Fürbringer (1900);
Eunota of Huxley (1886) and Furbringer (1900); Iguanomorpha of Fürbringer (1900); and Iguanoidae of Hay (1930).
Comments: Nineteenth and early twentieth century authors commonly recognized a group composed primarily or exclusively of species here referred to Iguania based on their short, thick tongues and thus excluding the highly modified Chamaeleonidae (e.g., Cuvier, 1817;
Latreille, 1825; Wagler, 1830; Gray, 1845; Cope, 1900; Camp, 1923). (The tendency to separate chamaeleonids reached an extreme in the sys- tems of Boulenger [1884, 1885–1887] and Hay [1902], who placed them in a taxon, Rhiptoglossa or Rhiptoglossi, separate from and of equal rank to a taxon containing all other lizards.) Some authors from this time period grouped chame- leons with other iguanians in a larger taxon that also included the similarly broad-tongued gekkotans (e.g., Gray, 1831; Fitzinger, 1843;
Camp, 1923; Hay, 1930). Others implied a close relationship by listing the taxa sequentially
(e.g., Laurenti, 1768; Blainville, 1822, 1835;
Bonaparte, 1841; Cope, 1889, 1900; Romer, 1945), though it is unclear whether they consid- ered all taxa now considered iguanians to be more closely related to one another than to any other lizards (a paraphyletic group). Fitzinger (1826) recognized a group, based on a dilatable throat, composed almost exclusively of iguanians (his Chamaeleonoidea, Pneustoidea, Draconoidea, and Agamoidea), though he also included dis- tantly related pterosaurs with gliding iguanian lizards (in his Draconoidea). Fitzinger did not name this group, nor did he recognize it in his later major work on the classification of rep- tiles (Fitzinger, 1843). Camp (1923) proposed that iguanids, agamids, and chamaeleonids shared an exclusive common ancestry, though he did not place all three together in an exclu- sive taxon. McDowell and Bogert (1954) placed chamaeleonids with agamids and iguanids in Iguania, and the exclusive common ancestry of these three taxa has been corroborated by sub- sequent explicit phylogenetic analyses based on both morphological (e.g., Estes et al., 1988; Lee, 1998; Reynoso, 1998; Gauthier et al., 2012) and molecular (e.g., Townsend et al., 2004; Vidal and Hedges, 2004; Pyron et al., 2013) data.
Phylogenetic analyses based on morphological data place Iguania as one of the two primary crown clades within Squamata (e.g., Estes et al., 1988; Schwenk, 1988; Lee, 1998; Gauthier et al., 2012); by contrast, those based on molecular sequence data have Iguania more deeply nested within Squamata (e.g., Townsend et al., 2004;
Vidal and Hedges, 2004; Pyron et al., 2013).
The name Iguania has been attributed to
Cuvier 1817 (e.g., Estes et al., 1988) and Latreille
1825 (e.g., Camp, 1923); however, Cuvier used
the name Iguaniens and Latreille used the name
Iguanii. According to Kuhn (1967), Cope (1864)
was the first author to use the name Iguania,
though he used it for his Anolidae plus Iguanidae
(see also Cope, 1875, 1889) so that his Iguania
corresponds to Iguanidae of other authors
(e.g., Gray 1827, 1845; Boulenger, 1884, 1885–1887) and his own later work (Cope, 1900). Camp (1923; see also Romer, 1945) used the name Iguania for a taxon com- posed of Iguanidae and Agamidae but not Chamaeleonidae (Rhiptoglossa); nevertheless, he considered chamaeleonids to be derived from within Iguania, sharing a more recent common ancestor with Agamidae than with Iguanidae (see his Figure p. 333). McDowell and Bogert (1954:136) added Chamaeleonidae to Iguania, an arrangement that has been followed by most subsequent authors (e.g., Romer, 1956, 1966; Underwood, 1971; Estes et al., 1988;
Frost and Etheridge, 1989; Lee, 1998; Zug et al., 2001; Pyron et al., 2013). Selection of the name Iguania for the crown clade in ques- tion is highly appropriate given that it is by far the most commonly used name for that clade and has previously been tied to it using explicit phylogenetic definitions (Estes et al., 1988; Lee, 1998). The main alternative name, Iguanomorpha Furbinger 1900, has been used at roughly 1/100 the frequency of Iguania and has been explicitly defined as the name of a more inclusive clade (Conrad, 2008).
Although molecular data support a basal dichotomy within Iguania leading to the crown clades Iguanidae and Acrodonta (Macey et al., 1997; Schulte et al., 2003; Pyron et al., 2013), the lack of morphological corroboration for the monophyly of Iguanidae (Etheridge and de Queiroz, 1988; Frost and Etheridge, 1989; Gauthier et al., 2012), and thus poten- tial uncertainty concerning the basal rela- tionships within Iguania, has led us to use a maximum-crown-clade definition rather than a simpler minimum-clade definition. Internal specifiers are the type species of the type gen- era of the three taxa within Iguania tradition- ally ranked as families (Iguanidae, Agamidae, and Chamaeleonidae); all three are included to
ensure that all three of those taxa are included in Iguania. Our definition designates a clade of identical composition in the context of alterna- tive hypotheses (i.e., to the reference phylog- eny) concerning the relationships of Iguania to other Squamata (e.g., Townsend et al., 2004; Vidal and Hedges, 2004; Pyron et al., 2013).
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Authors
Kevin de Queiroz; Department of Vertebrate Zoology; National Museum of Natural History;
Smithsonian Institution; Washington, DC 20560-0162, USA. Email: [email protected].
Omar Torres-Carvajal; Museo de Zoología; Escuela de Ciencias Biológicas; Pontificia Universidad Católica del Ecuador; Av. 12 de Octubre 1076 y Roca, Quito, Ecuador. Email: omartorcar@
gmail.com.
James A. Schulte, II; Division of Amphibians and Reptiles; National Museum of Natural History; Smithsonian Institution;
Washington, DC 20560-0162, USA. Email:
