GASTEROSTEIDAE

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 : 46

CROWN GASTEROSTEIDAE (39)

Node Calibrated. Divergence between Pungitius and Gasterosteus .

Fossil Taxon and Specimen. Gasterosteus cf. aculeatus from the Alta Mira Shale, Monterey Formation of Palos Verdes , California, USA (specimen LACM 150177 , Los Angeles County Museum of Natural History , Los Angeles, California, USA) .

Phylogenetic Justification. The Monterey Formation gasterosteid has not been included in a formal cladistic analysis, but its placement within Gasterosteus is supported by the presence of two elongate, free dorsal-fin spines and a complete series of lateral plates along the flank. Bell et al. (2009) have argued for a more precise association with G. aculeatus based on provenance, body size, the number of lateral plates, and the absence of proximal cusps on the anal-fin spine.

Minimum Age. 13.1 Ma

Soft Maximum Age. 41.3 Ma

Age Justification. Diatoms associated with the specimen of Gasterosteus cf. aculeatus are indicative of Subzone a of the Denticulopsis hustedtii - Denticulopsis lauta Zone , which is equivalent to the lower Mohnian regional stage (Bell et al., 2009: table 1). Estimates provided by Barron (2003) for first and last appearances of diatom species tightly constrain the age of the Gasterosteus from the Monterey Formation to between 13.1 and 13.3 Ma, corresponding to the Serravallian stage of the Miocene. We derived our minimum age of 13.1 Ma for crown Gasterosteus from this reported range.

Because the Gasterosteus from the Monterey Formation represents the earliest reliable fossil occurrence of Gasterosteidae (other examples summarized in Nazarkin et al., 2013), a soft maximum age for crown Gasterosteus must be sought outside the family. Molecular anlyses associate Gasterosteidae and its immediate allies ( Hypoptychidae , Aulorhynchidae ) with several families generally assigned to Scorpaeniformes in historical classifications ( Agonidae , Anoplopomatidae , Anarhichadidae , Bathymasteridae , Cottidae , Cryptacanthodidae , Cyclopteridae , Hexagrammidae , Liparidae , Pholidae , Rhamphocottidae , Stichaeidae , Trichodontidae , Zaproridae , Zoarcidae ; Smith and Wheeler, 2006; Betancur-R. et al., 2013; Near et al., 2013). These groups generally inhabit the North Pacific (Nelson, 2006) and are characterized by sparse fossil records restricted largely to the Neogene (Patterson, 1993b). This likely reflects the fact that the relatively few Cenozoic sites along the margins of the North Pacific that yield abundant articulated fish remains are principally Miocene in age or younger (e.g., Yabumoto and Uyeno, 1994; Bannikov, 2010; Fierstine et al., 2012; Nazarkin et al., 2013a). The oldest skeletal evidence for any of these lineages is material of Cottidae attributed to Cottus from the Oligocene (Rupelian) Argile de Boom, Belgium, although the reliability of this identification is questionable (Patterson, 1993b). In the absence of suitable deposits or extensive fossil histories of immediate relatives, a maximum age for crown Gasterosteidae can only be established arbitrarily. We propose a constraint of 41.3 Ma based on the maximum possible age of the Bartonian Gorny Luch locality in the north Caucasus. This assemblage yields nearly 40 families of marine teleosts (Bannikov, 2010), including the earliest Champsodontidae (Bannikov, 2004) , which are placed as members of a broader clade including gasterosteids and other cottoids (sensu Betancur-R. et al., 2013) in molecular phylogenies (Near et al., 2013). However, the fauna from Gorny Luch lacks either gasterosteids or their closest cottoid relatives (Bannikov, 2010). The base of the Bartonian is dated to 41.3 Ma, which we designate as a maximum age estimate for the origin of crown Gasterosteidae .

Discussion. We have followed the arguments of Bell et al. (2009) in aligning the Gasterosteus fossil from the Monterey Formation with G. aculeatus . However, it is possible that some of the diagnostic characteristics of the species that they cite are primitive, and that this fossil more properly calibrates a less nested node within Gasterosteidae . However, it is clear that derived features of the dorsal fin minimally place the Miocene specimen within total-group Gasterosteus , if not the crown.