Various phylogenetic analyses of different data congruently support a sister group relationship between the Fregatidae and Suloidea, i.e., a clade including the Sulidae, Phalacrocoracidae, and Anhingidae (Ericson et al. 2006; Mayr 2008b; Brown et al. 2008). Among others, these taxa share a greatly abbreviated tarsometa-tarsus, which is only about half of the length of the carpometacarpus, a distally protruding trochlea for the second toe, and a pectinate claw of the third toe (Mayr 2003a, 2008b). Within the Phalacrocoracidae the tarsometatarsal features are only
Fig. 7.1 Hypothesis on the phylogenetic relationships between Paleogene and extant representatives of the Plotopteridae, Sphenisciformes, Fregatidae, and Suloidea. Selected apomorphies: 1 tarsometatarsus greatly abbreviated, with distally protruding trochlea for the second toe; 2 palatine with well-developed caudolateral angle, dorsal tympanic recess greatly enlarged and situated rostrally to the articular facets of the quadrate (except in Phalacrocoracidae and Anhingidae), claw of the third toe distinctly pectinate on its medial side; 3 palatine flat horizontal plate, 13 or fewer sclerotic ossicles, orbital process of quadrate reduced; 4 interzygapophysial lacunae of caudal cervical vertebrae of the first section very shallow, costal processes of cervical vertebrae of the second section greatly elongated, cnemial crests of the tibiotarsus strongly proximally protruding; 5 upper beak and mandible dorsoventrally deep and with numerous impressions of blood vessels, marked dorsal tympanic recess; 6 tarsometatarsus measuring less than one third of the carpometa-carpus, deltopectoral crest of the humerus triangular and protruding; 7 proximal end of the humerus deep and rounded, with ventrally directed humeral head, distal end of the humerus strongly flattened and ventrally protruding, scapulotricipital and humerotricipital sulci very deep and shifted toward the ventral margin of the humerus, scapula forming a thin, sheet-like, greatly expanded blade; 8 skull with marked supraorbital fossae for salt glands; 9 proximal vascular foramina of tarsometatarsus situated in very deep, elongate fossae on the dorsal surface of the tarsometatarsus; 10 distal vascular foramen of the tarsometatarsus lost; 11 acromion of the scapula greatly elongated and narrow (unknown for Phocavis); 12 distal vascular foramen of the tarsometatarsus lost. (After Mayr 2005b, 2007c, 2008b; phylogeny of Paleogene Sphenisciformes simplified after Ksepka et al. 2006, who did not list apomorphies of the nodes)
present in the small Microcarbo species, which are probably outside a clade formed by all other extant cormorants (Mayr 2007c).
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