Norberto E. Vaccari

Ontogeny and systematics of Toernquistiidae (Trilobita, Proetida) from the Ordovician of the Argentine Precordillera

The following new Toernquistiidae from Whiterockian (Llanvirn to lower Caradoc) strata of the Precordillera, western Argentina, are described: Chomatopyge canasi new species, Lasarchopyge benedettoi new genus and species, Lasarchopyge correae new genus and species, Lasarchopyge new species A, and Paratoernquistia sanchezae new genus and species. Phylogenetic analysis suggests that the Toernquistiidae Hupe, 1953 (including Chomatopyge, Lasarchopyge, Mesotaphraspis, Paratoernquistia, and Toernquistia) is closely related to but distinct from the Dimeropygidae Hupe, 1953 (including Ischyrotoma, Ischyrophyma and Dimeropyge). It is difficult to find unique synapomorphies that unite toernquistiids and dimeropygids into a monophyletic group that excludes other proetides (e.g., hystricurids), although details of their ontogenies are similar. Several species of Toernquistiidae are known from the Argentine Precordillera (one species previously described), and other species of this family have been described from Australia, Baltica, China, Kazakhstan and Laurentia. Members of the Dimeropygidae are known only from Baltica and Laurentia.

ONTOGENY OF THE PROETOID TRILOBITE STENOBLEPHARUM, AND RELATIONSHIPS OF A NEW SPECIES FROM THE UPPER ORDOVICIAN OF ARGENTINA

Silicified material from the Early Caradoc part of the Las Aguaditas Formation in San Juan Province, Argentina, includes a nearly complete growth series for a new species of the tropidocoryphid Stenoblepharum Owens, 1973. Cladistic analysis of Stenoblepharum species indicates that S. astinii new species is most closely allied to the Early Caradoc S. strasburgense (Cooper, 1953) from Virginia. Chinese species of Stenoblepharum are sister group to a Baltic/Laurentian clade. A single adult-like protaspid stage occurs in the life cycle of S. astinii, closely resembling the protaspis of Decoroproetus. It is preceded by a non-adult-like first protaspid instar that appears to be characteristic of Proetoidea in general but contrasts markedly with the early larval stages of other taxa in Proetida.

Ontogenies of some Ordovician Telephinidae from Argentina, and larval patterns in the Proetida (Trilobita)

The ontogenies of three new species of Telephinidae, Telephina calandria, Telephina chingolo , and Telephina problematica are described from Arenig-Caradoc strata in the Argentine Precordillera, and compared with the larval stages of some other Proetida, including other telephinids. New findings reveal 1) a radical metamorphosis in the ontogenies of these Telephina species late in the meraspid period, not previously described among Trilobita; and 2) distinctive hypostomes of Telephinidae containing long, thin anterolaterally and dorsally splayed anterior wings. Early ontogenies of different species currently assigned to the genus Telephina fall into at least two distinct morphological and life history groups, and hypostomes (if correctly assigned in previous works) vary significantly. The three new species strengthen the hypothesis of a phylogenetic connection between Oopsites and Telephina. Three morphological types of protaspid instars are described for proetide trilobites. Two are anaprotaspides, and the third is a metaprotaspis. They always occur in the same sequence in the ontogeny, but no cases are known of all three types in the same species. These larval types are important for understanding the systematics and life cycles of the Proetida. Benthic/pelagic transitions identify four life history patterns among the the Proetida. The best larval synapomorphy for the Proetida is the distinctive metaprotaspid larval type, which is absent in very few proetides (some Telephinidae), perhaps as a result of heterochronic displacement of this stage into the meraspid period.

SYSTEMATICS OF SHUMARDIIDAE (TRILOBITA), WITH NEW SPECIES FROM THE ORDOVICIAN OF ARGENTINA

Abstract New shumardiid trilobites from Arenig to Early Caradoc deposits of the Argentine Precordillera include species of a revised Kweichowilla (K. salasae, K. sterrenae, and K. piojensis) and the new genus Changchowilla (C. sanjuanina and C. gracielae, and C.? carrerai). Conophrys fabiani new species occurs in the Early Tremadoc of the western Puna region, northwestern Argentina. Leoforteyia new genus is based on L. hintzei new species from the Ibexian of Utah. Published taxa recognized as new species are Conophrys rushtoni, Conophrys wrighti, Leoforteyia ludvigseni and Shumardia whittingtoni. Phylogenetic analysis suggests the differentiation of Shumardia Billings, 1862; Kweichowilla Chang, 1964; Changchowilla new genus; and Leoforteyia new genus as separate taxa and indicates that Conophrys Callaway, 1877, is a grade group. Silicified material provides a nearly complete growth series for Kweichowilla salasae, including the first protaspides known with confidence for the Shumardiidae. Additionally, ontogenetic material for K. sterrenae, C. sanjuanina, C. riojana (Benedetto and Cañas) and C.? carrerai is described. Leoforteyia is restricted to the Ibexian-Whiterockian of western Laurentia; species of Shumardia are widespread in the Arenig to Early Ashgill of western Europe, Australia, Laurentia, China and Russia. Changchowilla is recorded in the mid-Late Arenig-Llanvirn of the Precordillera and in the Llanvirn-middle Caradoc of China. Argentine species of Kweichowilla are closely allied to Australian species, suggesting biogeographic affinities of the Precordillera to the eastern margin of Gondwana by the Llanvirn and Caradoc. Functional morphology, occurrence in fine grained sediments, and association mainly with atheloptic and pelagic trilobites suggest that shumardiids were deposit-feeders that inhabited low light levels in low energy settings, with a limited ability to burrow in soft sediments.

Ontogeny and relationships of the Ordovician odontopleurid trilobite Ceratocara, with new species from Argentina and New York

A growth series is described for a new species of Ceratocara Ramskold, 1991, C. argentina, from the Upper Ordovician (Caradoc) part of the Las Aguaditas Formation, near Jachal in San Juan Province, Argentine Precordillera. Another new species of Ceratocara, C. shawi, is described from the Middle Ordovician (lower Chazy) Crown Point Formation of New York. A phylogenetic analysis is presented for these species, other well-known Ordovician species of Ceratocara, and some Ordovician species of Ceratocephala, with Ceratocephalina tridens Whittington, 1956, as outgroup. The analysis presented supports the monophyly of both Ceratocara and Ceratocephala Warder, 1838, their divergence having occurred by the middle Arenig. The ontogenies of the Ceratocara species from Argentina and New York, complete from protaspid to holaspid growth stages, are some of the best preserved odontopleurid ontogenies described to date. Material of Ceratocephala triacantheis Whittington and Evitt, 1954, from the Crown Point Formation of the Chazy Group of New York, is discriminated from that of Ceratocara shawi.

Cambrian origins and affinities of an enigmatic fossil group of arthropods.

Euthycarcinoids are one of the most enigmatic arthropod groups, having been assigned to nearly all major clades of Arthropoda. Recent work has endorsed closest relationships with crustaceans or a myriapod–hexapod assemblage, a basal position in the Euarthropoda, or a placement in the Hexapoda or hexapod stem group. Euthycarcinoids are known from 13 species ranging in age from Late Ordovician or Early Silurian to Middle Triassic, all in freshwater or brackish water environments. Here we describe a euthycarcinoid from marine strata in Argentina dating from the latest Cambrian period, extending the groups record back as much as 50 million years. Despite its antiquity and marine occurrence, the Cambrian species demonstrates that morphological details were conserved in the transition to fresh water. Trackways in the same unit as the euthycarcinoid strengthen arguments that similar traces of subaerial origin from Cambro-Ordovician rocks were made by euthycarcinoids. Large mandibles in euthycarcinoids are confirmed by the Cambrian species. A morphology-based phylogeny resolves euthycarcinoids as stem-group Mandibulata, sister to the Myriapoda and Crustacea plus Hexapoda.

Ordovician pliomerid and prosopiscid trilobites from Argentina

Pliomerina Chugaeva, 1958, a characteristic element of the peri-Gondwanan Eokosovopeltis-Pliomerina Province, occurs in Llanvirn and Caradoc strata of the Argentine Precordillera. Three protaspid instars are present in the ontogeny of the Early Caradoc Pliomerina peripata new species. A species possibly representing Pliomerella is a rare element in Early Caradoc strata of the Las Aguaditas Formation. Prosopiscus is represented by a Llanvirn species with a first record of protaspid larvae for the enigmatic Family Prosopiscidae. Early growth stages support closest relations of prosopiscids to Phacopina. The presence of Pliomerina and Prosopiscus , along with the cheirurid Pateraspis , demonstrates a peri-Gondwanan influence on the Precordilleran fauna by the Llanvirn, and supports the proximity of the Precordillera terrane to the South American margin by that time.

Ordovician (Whiterock) calymenid and encrinurid trilobites from the Precordillera of Argentina

Phacopida from upper Whiterock (Lower Caradoc) horizons in the Las Aguaditas Formation of San Juan Province, Ar- gentina, include the calymenid Platycalymene trapezoidalis (Baldis and Pothe, 1995) and the encrinurids Frencrinuroides edseli new species, Lasaguaditas oweni new genus and species, and Walencrinuroides? new species A. Sulcocalymene Baldis and P6the, 1995, a purported subgenus of Flexicalymene, is a junior subjective synonym of Platycalymene Shirley, 1936. Platycalymene is now known from Avalonia, Baltica, Laurentia (Scotland), and the Precordillera. Emending the cladistic analysis of Ordovician Encrinurinae by Lesperance and Desbiens (1995), the monophyly and membership of Frencrinuroides and Walencrinuroides are ambiguous. Frencrin- uroides edseli is closely related to species from eastern Laurentia. Lasaguaditas new genus is superficially cybelinid-like in some respects but shares several derived characters with the Encrinurinae. All three encrinurinid species in the Las Aguaditas Formation possess two instars in the protaspid period, a general pattern in Ordovician encrinurinid ontogeny.

Ordovician cheirurid trilobites from the Argentine Precordillera

New cheirurid trilobite species from the Las Aguaditas Formation in San Juan Province include the Llanvirn Macrogrammus rafi, and the Early Caradoc Ceraurinella zhoui, Nieszkowskia jakei, and N. yongyii. Precordilleran species, such as the Llanvirn Macrogrammus pengi new species from the Gualcamayo Formation, reinforce sinoparapilekiinid affinities for the poorly known Macrogrammus Whittard, 1966, although the monophyly of Sinoparapilekiini requires corroboration. The ontogeny of Ceraurinella zhoui confirms the presence of early protaspid stages for this genus (and Cheirurinae in general). Rare cheirurids include species of Heliomeroides, Pateraspis, and an additional acanthoparyphinid.

Lower Devonian calmoniid trilobites from the Argentine Precordillera: new taxa of the Bouleia Group, and remarks on the tempo of calmoniid radiation

New calmoniids from the Lower Devonian Talacasto Formation in the Precordillera of San Juan, Argentina, extend the stratigraphic and geographic ranges of a clade including Bouleia Kozlowski, 1923 and Parabouleia Eldredge, 1972. The new genus Talacastops accommodates the Lochkovian T. zarelae sp.nov. from the Talacasto Formation and a closely related species from western Bolivia ( Talacastops sp.nov. A). The diagnosis of Parabouleia is broadened to include P. eldredgei sp.nov., from Lochkovian strata in the lower part of the Talacasto Formation. Calmoniids from below the Scaphiocoelia Assemblage Zone display morphological disparity that rivals later occurrences, and do not conform to a model of gradual transformation of an acastomorph ancestor. Stratigraphic range extensions based on correction for ghost lineages imply a high diversity within Calmoniidae very early in the Devonian.