DALMANITIDAE Vogdes, 1890

Randolfe, Enrique A., Rustán, Juan José & Bignon, Arnaud, 2022, New dalmanitid trilobite taxa from the Lower Devonian of Argentina: comments on spinosity in endemic taxa from southern high paleolatitudes, Comptes Rendus Palevol 21 (2), pp. 17-38 : 20

Family DALMANITIDAE Vogdes, 1890

REMARKS

Subfamilies of Dalmanitidae have long been discussed. For Silurian and Devonian taxa, the most widely accepted groups include Dalmanitinae Vogdes, 1890 and Synphoriinae Delo, 1935. In particular, Synphoriinae was considered either a distinct family ( Delo 1935; Lespérance 1975), or a subfamily closely related to Dalmanitinae ( Lespérance & Bourque 1971; Holloway 1981; Edgecombe 1993; Holloway & Carvalho 2009). Currently, the proposals of subfamilies by Holloway (1981) along with characters proposed by Campbell (1977) are the most frequently used for classification.Dalmanitinae is defined mainly by apodems of S1 equidistant between those of SO and S2; a cephalic epiborder furrow; large exsag. eyes extending close to the posterior border furrow; a well-developed pygidial border; a pygidium with 12 or more axial rings; and anterior pleural bands sloping steeply posteriorly and posterior ones sloping more gently anteriorly on the pygidial pleural furrows which are asymmetrical in cross section. On the other hand, Synphoriinae is mainly supported by the exsagittal distance between S1 and S2 apodems 1.5 times longer than between S1 and SO apodems; S2 reduced tr. tending to be subcircular; shorter exsag. eyes; pygidium without a well-defined border; pygidial pleural bands of equal length exsag. with a symmetrical pleural furrow in cross section; and apodemal pits of inter-ring furrows without contacting axial furrows on the pygidium. However, some taxonomic issues remain unsolved, so that several genera cannot be clearly assigned to a subfamily based on their current definitions ( Edgecombe 1991; Rustán & Vaccari 2012). For example, a number of characters is demonstrably variable within a single genus, such as the spacing between apodems of the glabellar furrows in Lygdozoon Holloway, 1981 , from the Silurian of the United States. Additionally, the diagnosis of Synphoriinae does not consider the absence of a cephalic epiborder furrow or the number of pygidial axial rings ( Holloway 1981), in order to classify taxa as Lygdozoon . In spite of this, such characters are still usually considered diagnostic of Dalmanitinae. In our case, we recognize a combination of character states of more than one subfamily in some new taxa proposed herein.Consequently, pending a complete phylogenetic analysis of Dalmanitidae in order to clarify their taxonomy, in the present contribution we do not propose subfamilial assignments for these new taxa. In discussions, for matter of ease, we refer to Dalmanitinae and Synphoriinae taking into account considerations given by Holloway (1981).