Gasterosteus

Benton, MJ, Donoghue, PCJ, Vinther, J, Asher, RJ, Friedman, M & Near, TJ, 2015, Constraints on the timescale of animal evolutionary history, Palaeontologia Electronica (Florence, Italy) 15 (1), pp. 1-107 : 45

GASTEROSTEUS – TETRAODON , TAKIFUGU (38)

Node Calibrated. Divergence between Gasterosteidae and Tetraodontiformes . This corresponds to an unnamed clade within Percomorpha.

Fossil Taxon and Specimen. Cretatriacanthus guidottii from the ‘Calcari Melissano’ (of historical usage) at Canale near Nardò, Italy (holotype MCSNV 1377 , Museo Civico di Storia Naturale , Verona, Italy) .

Phylogenetic Justification. There are several reports of Cretaceous tetraodontiforms (Patterson, 1993b; Tyler and Sorbini, 1996; Santini and Tyler, 2003; Gallo et al., 2009; Friedman, 2012; Tyler and Križnar, 2013). We select Cretatriacanthus , from Nardò, Italy as a conservative minimum constraint for the divergence between Tetraodontiformes and Ovalentaria. Cretatriacanthus represents the youngest putative tetraodontiform of Cretaceous age represented by body-fossil remains. The absence of an elaborate dermal carapace in Cretatriacanthus means that key tetraodontiform features like the absence of pleural ribs and geometry of the pelvic girdle are readily apparent in this genus, whereas they are generally obscured by an elaborate bony carapace in other Cretaceous examples.

Minimum Age. 69.71 Ma

Soft Maximum Age. 130.8 Ma

Age Justification. The fish-bearing limestones at Nardò are generally referred to the ‘Calcari di Melissano’, a name historically applied to the Late Cretaceous platform carbonates of Salento (Martinis, 1967). However, usage has since been restricted to one part of the Late Cretaceous carbonate succession in the Apulian platform (e.g., Bosellini and Parente, 1994; Schlüter et al., 2008). Medizza and Sorbini (1980) provide a list of calcareous nannofossil species recovered from the fish-bearing layers, the most biostratigraphically relevant of which is Uniplanarus trifidus (reported as Quadrum trifidum ). The first appearance of this species marks the beginning of Calcareous Nannoplankton Zone CC23, and it makes its last appearance in the middle of CC24. The top of CC24 is roughly equivalent to the top of the Baculites clinolobatus Ammonite Zone of the Western Interior Seaway, which contains a bentonite horizon dated as 70.08 Ma ± 0.37 Myr. It is from this value that we derive our minimum age estimate of 69.71 Ma.

Percomorphs, and acanthomorphs more generally, are unknown from a series of fish faunas of mid-late Early Cretaceous age that represent a range of depositional settings from fully marine to lacustrine: the Gault Clay of England (Albian; Gale and Owen, 2010; Forey and Longbottom, 2010; Nolf, 2010), Helgoland in Germany (Aptian; Taverne, 1981b), the Crato Formation of Brazil (Martill, 1993; early interpretations of Araripichthys as a lampridiform have been decisively rejected by Patterson, 1993a and Maisey and Moody, 2001), and the Coquiero Seco Formation of Brazil (Gallo and Cohelo, 2008). The oldest of these deposits, the Coquiero Seco Formation of Brazil, yields the oldest putative representative of Eurypterygii (the clade containing Aulopiformes, Myctophiformes, and Acanthomorpha), and provides the basis for our estimated maximum age divergence between Tetraodontiformes and Gasterostidae. The Barremian is dated to approximately 130.8-126.3 Ma (Ogg et al., 2012b); we derive our soft maximum from the oldest limit.

Discussion. Gasterosteiform fishes are classically considered to include gasterosteids (sticklebacks) plus syngnathoids (pipefishes and allies), pegasids (sea moths), aulorhynchids (tubesnouts), hypotychids (sand eel), and, in some classications, indostomids (armored sticklebacks; Pietsch, 1978; Kievany and Nelson, 2006). The monophyly of this assemblage to the exclusion of other acanthomorph clades is rejected decisively by molecular evidence, and its constitutent members have been redistributed within Percomorpha. Syngnathoids and pegasids do appear to be closely related, but they are not resolved as immediate sister taxa (Smith and Wheeler, 2006; Betancur-R. et al., 2013; Near et al., 2013). The clade containing syngnathoids and pegasids is placed among the earliest-diverging percomorph radiations, and other members of the classical Gasterosteiformes are far removed from these taxa. Gasterosteids, hypotychids, and aulorhynchids form a clade in an apical position within Percomorpha and are associated with some taxa classically assigned to Scorpaeniformes , while Indostomus is resolved as a close relative of mastacembalids (swamp eels) (e.g., Smith and Wheeler, 2006; Kawahara et al., 2008; Li et al., 2009; Near et al., 2012, 2013; Wainwright et al., 2012; Betancur-R. et al., 2013). As a consequence, fossil specimens listed as gasterosteiforms in previous reviews of calibrations do not provide suitable fossil-based minimum ages for the Oryzias , Cichlidae – Gasterosteus, Takifugu, Tetraodon divergence. Gasterorhamphosus has been cited in this context as providing a minimum age for the gasterosteiform lineage (Benton and Donoghue, 2007, p. 41; Benton et al., 2009, p. 65). However, it is clear that this fossil, which derives from the same beds at Nardò, Italy as Cretatriacanthus (Sorbini, 1981) , is a syngnathoid and thus not closely related to Gasterosteus . Our reasons for selecting Cretatriacanthus rather than other Late Cretaceous fossils as a constraint for the origin of Tetraodontiformes are outlined in the discussion for Node 35.