Discussion of Phylogenetic Relationships
© 1987 Theodore W. Pietsch
That the order Lophiiformes constitutes a natural assemblage seems certain. All included taxa share at least six unique and morphologically complex synapomorphic features (numbered 1 through 6 in the cladogram; a modification of Pietsch, 1981, 1984a):
- Spinous dorsal fin primitively of six spines, the anterior-most three of which are cephalic in position, the first modified to serve as a luring apparatus (involving numerous associated specializations, e.g., a medial depression of the anterior portion of the cranium, loss of the nasal bones and supraoccipital lateral-line commissure, and complex modifications of associated musculature and innervation);
- Epiotics separated from the parietals and meeting on the midline posterior to the supraoccipital;
- Gill opening restricted to a small, elongate, tube-like opening situated immediately dorsal to, posterior to, or ventral to (rarely partly anterior to) the pectoral-fin base;
- A single hypural plate emanating from a single complex half-centrum;
- Ventralmost pectoral radial considerably expanded distally (Pietsch, 1981: 397, 411, figs. 14, 40); and
- Eggs spawned in a double, scroll-shaped mucous sheath (Rasquin, 1958; Pietsch and Grobecker, 1987: 351).
Since Regan (1912), three major lophiiform taxa of equal rank have been recognized by nearly all authors. These taxa, together with their currently recognized families (the 11 families of the meso- and bathypelagic Ceratioidei excluded; see Bertelsen, 1951: 29; and Pietsch, 1972: 18), are as follows:
- Suborder Lophioidei
- Family Lophiidae
- Suborder Antennarioidei
- Family Antennariidae
- Family Tetrabrachiidae
- Family Lophichthyidae
- Family Brachionichthyidae
- Family Chaunacidae
- Family Ogcocephalidae
- Suborder Ceratioidei
Pietsch (1981: 416, fig. 41) attempted to test the validity of Regan's (1912) concept of three major lophiiform taxa by using cladistic analysis. In that study, serious difficulty was encountered in efforts to establish monophyly for the six families of Regan's (1912) Antennarioidei. Although a number of synapomorphic features were found to support a sister-group relationship between the four families Antennariidae through Brachionichthyidae, and between the families Chaunacidae and Ogcocephalidae, no convincing synapomorphy was found to link these two larger subgroups.
In a more recent attempt, Pietsch and Grobecker (1987: 268, fig. 110) proposed a new cladogram, which, in resolving the former difficulties, differed significantly from that previously published (Pietsch, 1981, fig. 41). In this revised cladogram, the suborder Antennarioidei is restricted to just four families: the Antennariidae, recognized as the sister-group of the Tetrabrachiidae, these two families together forming the sister-group of the Lophichthyidae, and this assemblage of three families forming the sister-group of the Brachionichthyidae. These relationships are supported by a total of seven synapomorphies, most of which were previously described by Pietsch (1981):
- Posteromedial process of the vomer emerging from the ventral surface as a laterally compressed, keel-like structure, its ventral margin (as seen in lateral view) strongly convex (1981: 397, figs. 4-6);
- Postmaxillary process of the premaxilla spatulate (1981: 398, figs. 8, 20);
- Opercle similarly reduced in size (1981: 401, figs. 9, 21);
- Ectopterygoid triradiate, a dorsal process overlapping the medial surface of the metapterygoid (1981: 400, figs. 9, 21, 22);
- Proximal end of hypobranchials II and III deeply bifurcate (1981: 407, figs. 11, 28, 29);
- Interhyal with a medial, posterolaterally directed process that makes contact with the respective preopercle (1981: 400, fig. 26);
- Illicial pterygiophore and pterygiophore of the third dorsal spine with highly compressed, blade-like dorsal expansions (1981: 410, figs. 36, 37).
The present interpretation of lophiiform relationships differs further from any previously proposed hypothesis in considering the Antennarioidei (sensu stricto) to form the primitive sister-group of a much larger group that includes the Chaunacoidei, the Ogcocephaloidei, and the Ceratioidei. The Ogcocephaloidei are in turn recognized as the primitive sister-group of the Ceratioidei.
Monophyly for a group containing the suborders Antennarioidei, Chaunacoidei, Ogcocephaloidei, and Ceratioidei is supported by four synapomorphies, all previously identified by Pietsch (1984a):
- Eggs and larvae small (at all stages the eggs are considerably less than 50% the diameter of those of lophioids; the smallest larvae are certainly less than 50%, and probably less than 30%, the size of those of lophioids; size at transformation to the prejuvenile stage is less than 60% that of lophioids; Pietsch, 1984a, fig. 164);
- Head of larvae proportionately large relative to the body (always greater than 45% SL, compared to less than 30% in lophioids; Pietsch, 1984a, fig. 164);
- Number of dorsal-fin spines reduced from a primitive six in lophioids to three or less (Pietsch, 1981: 409, figs. 36-38);
- Pharyngobranchial IV absent (present and well toothed in lophioids; Pietsch, 1981: 401, figs. 11, 28-32).
Monophyly for a group containing the suborders Chaunacoidei, Ogcocephaloidei, and Ceratioidei is supported by two synapomorphies:
- Second dorsal-fin spine reduced and embedded beneath skin of the head (Pietsch, 1981: 410, figs. 36-38);
- Gill filaments of gill arch I absent (but present on proximal end of ceratobranchial I of some ceratioids; Bradbury, 1967: 408; Pietsch, 1981: 415).
Monophyly for a group containing the Ogcocephaloidei and Ceratioidei is supported by four synapomorphies:
- Second dorsal-fin spine reduced to a small remnant (well developed in all other lophiiforms and secondarily developed in the ceratioid families Diceratiidae and Ceratiidae; Bertelsen, 1951: 17; Pietsch, 1981: 410, fig. 38);
- Third dorsal-fin spine and pterygiophore absent (present in all other lophiiforms; Bertelsen, 1951: 17; Bradbury, 1967: 401; Pietsch, 1981: 410, fig. 38);
- Epibranchial I simple, without ligamentous connection to epibranchial II (in batrachoidiforms and all other lophiiforms, epibranchial I bears a medial process ligamentously attached to the proximal tip of epibranchial II; Pietsch, 1981: 401, figs. 28-32);
- Posttemporal fused to cranium (attached to the cranium in batrachoidiforms and all other lophiiforms in such a way that considerable movement in an anterodorsal-posteroventral plane is possible; Pietsch, 1981: 411).
Of the possible cladograms that could be constructed on the basis of the data provided, the hypothesis presented is by far the most parsimonious (but see Pietsch, 1984a: 324, for a discussion of convergence or reversal of character states).
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