The Upper Ordovician trinucleid trilobiteBancroftolithusfrom the Precordillera of Argentina

Abstract

The trinucleid trilobite Bancroftolithus Baldis and Pöthe, 1995 includes a group of species from Sandbian strata of the Argentine Precordillera. The monotypic Hunickenolithus Baldis and Pöthe, 1995 from the Las Aguaditas Formation at its type locality in San Juan Province is placed in the synonymy of Bancroftolithus. Of four nominal taxa from the Las Aguaditas Formation, B. pozensis Baldis and Pöthe, 1995, and B. hughesi Baldis and Pöthe, 1995 are retained, and both are revised based on new collections from the type locality that include ontogenetic series from the protaspid period. Two protaspid stages are recognized in both species. Three additional species (Bancroftolithus alki n. sp., B. cf. B. pozoensis, Bancroftolithus sp.) from broadly coeval strata in the Las Plantas Member of the Las Vacas Formation in La Rioja Province are identified as the closest relatives of the Las Aguaditas species. Bancroftolithus alki also occurs in the Los Azules Formation in San Juan Province. The five species included in this regional clade exhibit significant morphological differences in the lower lamellae, an unusual feature among the Trinucleidae. Bancroftolithus is evidently most closely related to the Australian Katian genus Parkesolithus. The two are not convincingly assigned to any of the existing trinucleid subfamilies.

Ontogeny of a New Species of the Cambrian Series 3 (Middle Cambrian) Trilobite Genus Liostracina Monke, 1903 from North China and the Taxonomic Position of the Superfamily Trinucleoidea

“…Ordovician trinucleoidean protaspides have been documented several times (Whittington, 1959;Shaw, 1968;Fortey and Chatterton, 1988;Speyer and Chatterton, 1989;Chatterton et al, 1994;Waisfeld et al, 2011). All of these protaspides are highly convex, so that they were regarded as ''asaphoid'' protaspides (Chatterton et al, 1994) which must have undergone a radical metamorphosis between the protaspid and meraspid periods (Fortey and Chatterton, 1988;Chatterton and Speyer, 1997).…”

Lower middle Darriwilian (Ordovician) graptolites and index conodonts from the Central Precordillera of San Juan Province, Argentina

“…There are many studies on fossils from the Las Aguaditas Formation such as, bryozoans, brachiopods, nautiloids (Carrera, ; Carrera & Ernst, ), trilobites (Waisfeld, Vaccari, Edgecombe, & Chatterton, ), and ostracods (Salas, ). The first graptolites recorded from this unit were Dicellograptus divaricatus salopiensis Elles and Wood in association with Dicranograptus nicholsoni Hopkinson (Blasco & Ramos, ).…”

Hydrodynamic function of genal prolongations in trinucleimorph trilobites revealed by computational fluid dynamics

“…In comparison, trinucleids appear to have lived in predominantly deeper waters, having often lost the visual structures (Hughes et al, 1975). Trinucleids are frequently found in black shales and fine sandstones (Miller, 1972; Fortey and Gutiérrez-Marco, 2022), though some might have lived slightly shallower (Waisfeld et al, 2011), or are preserved in distal turbidites (Ghobadi Pour, 2022).…”