Aves Sangster, 2005, new clade name

Daedalornithes, new clade name

Definition: The name Daedalornithes, as defined here, refers to the least inclusive clade comprising Aegotheles cristatus (White) and Apus apus (Linnaeus). Aegotheles cristatus and Apus apus are selected as reference taxa because these are the type species of Aegotheles and Apus, respectively, on which the names Aegothelidae, and Apodidae and Apodiformes, respectively, are based. The definition is based on the principles of phylogenetic taxonomy (de Queiroz & Gauthier 1992). Use of two reference taxa, an owlet­nightjar and a swift, guarantees that the name always refers to a monophyletic group that minimally includes Aegotheles owlet­nightjars and Apus swifts. Because the definition refers to the least inclusive (i.e. smallest) monophyletic group specified by these two taxa, it excludes all taxa that are placed outside this clade. A node­ rather than a stem­based definition of Daedalornithes is selected because its sister­taxon is not resolved (see below), as recommended by Sereno (1999).

Description: Mayr (2002) identified six morphological synapomorphies of Daedalornithes: (i) os palatinum with greatly protruding angulus caudolateralis; (ii) processus basipterygoidei reduced; (iii) pneumatic foramina on the caudal surface of the processus oticus; (iv) extremitas omalis of coracoid hooked and processus lateralis greatly reduced; (v) musculus splenius capitis with cruciform origin; (vi) caeca absent. Mayr et al. (2003) identified two additional morphological synapomorphies: (vii) processus terminalis ischii of pelvis very narrow and slender, touching pubis at an angle of 45–90°, fenestra ischiopubica very wide; (viii) musculus fibularis longus absent. They identified character (v) as an unambiguous synapomorphy and characters (iii), (iv) and (vi) to (viii) as synapomorphies that, although not unique to Daedalornithes, are optimized in their phylogenetic analysis as independently derived in the common ancestor of this clade.

Taxonomic content: Based on current knowledge (Mayr 2002; Mayr et al. 2003; Cracraft et al. 2004), the name Daedalornithes refers to a clade that, among extant taxa, only includes Aegothelidae (owlet­nightjars), Hemiprocnidae (tree swifts), Apodidae (swifts) and Trochilidae (hummingbirds).

The extinct Scaniacypselus, Jungornis, Argornis and Parargornis are not currently regarded as (crown­group) members of Aegothelidae, Hemiprocnidae, Apodidae or Trochilidae but are part of Daedalornithes based on phylogenetic analysis or the possession of shared derived characters (see Mayr & Manegold 2002; Mayr 2003a, 2003b). The position of the extinct Aegialornis and Eocypselus relative to Aegothelidae, Apodiformes and Podargidae and, hence their inclusion in Daedalornithes, is unresolved (Mayr 2003a). Two other extinct taxa, Laputavis and Primapus, were included in Apodiformes by Dyke (2001) but the relationships suggested in this study are considered to be doubtful due to problems with character coding (Mayr 2001).

Phylogenetic relationships: The relationships of Daedalornithes with other birds are as yet unresolved. A morphological study (Mayr 2002) suggested that Daedalornithes is the sister­group of (Nyctibiiidae + Caprimulgidae). This study included only eight ingroup taxa and was therefore not designed to exclude other taxa as potential sister­groups of Daedalornithes. Analysis of an expanded data set (Mayr et al. 2003) also identified (Nyctibiidae + Caprimulgidae) as the sister taxon of Daedalornithes but bootstrap support for this grouping was less than 50%. Maximum Parsimony analysis of DNA sequences of three nuclear genes placed Daedalornithes in an unresolved polytomy with Passeriformes and numerous non­passerine groups. Bayesian analysis of the same molecular data set identified Podargidae as the sister taxon of Daedalornithes but with low posterior probability (58%). Combined analysis of morphological and molecular data sets placed Daedalornithes in an unresolved trichotomy with Nyctibiidae and Caprimulgidae, again with low support (50%). A study based on the nuclear gene c­myc (Harshman, Braun & Huddleston in Cracraft et al. 2004) suggested that Trogonidae is the sister­group of Daedalornithes but bootstrap support was not indicated. Two other studies (summarized in Cracraft et al. 2004) could not resolve the sister­group of Daedalornithes. Daedalornithes is therefore best considered as incertae sedis among the ‘higher land bird’ assemblage.

Taxonomic sequence: Due to the unresolved relationships among ‘higher land birds’, no changes are warranted in the position of Daedalornithes in linear sequences. Thus, I suggest that Daedalornithes is listed after Steatornithidae, Nyctibiidae and Caprimulgidae (cf Dickinson 2003). To reflect their phylogenetic relationships, the taxa included in Daedalornithes are best arranged in the following sequence: Aegothelidae, Hemiprocnidae, Apodidae, Trochilidae.

Etymology: The clade is named after Daedalus, the Greek mythological figure who fabricated wings and improved these until these allowed him and his son Icarus to soar upwards into the air. The name is appropriate in view of the great flight capabilities that evolved within the clade.