David K. Brezinski

The rise and fall of late Paleozoic trilobites of the United States

Based on range data and generic composition, four stages of evolution are recognized for late Paleozoic trilobites of the contiguous United States. Stage 1 occurs in the Lower Mississippian (Kinderhookian-Osagean) and is characterized by a generically diverse association of short-ranging, stenotopic species that are strongly provincial. Stage 2 species are present in the Upper Mississippian and consist of a single, eurytopic, pandemic genus, Paladin. Species of Stage 2 are much longer-ranging than those of Stage 1, and some species may have persisted for as long as 12 m.y. Stage 3 is present within Pennsylvanian and Lower Permian strata and consists initially of the eurytopic, endemic genera Sevillia and Ameura as well as the pandemic genus Ditomopyge. During the middle Pennsylvanian the very long-ranging species Ameura missouriensis and Ditomopyge scitula survived for more than 20 m.y. During the late Pennsylvanian and early Permian, a number of pandemic genera appear to have immigrated into what is now North America. Stage 4 is restricted to the Upper Permian (late Leonardian-Guadalupian) strata and is characterized by short-ranging, stenotopic, provincial genera. The main causal factor controlling the four-stage evolution of late Paleozoic trilobites of the United States is interpreted to be eustacy. Whereas Stage 1 represents an adaptive radiation developed during the Lower Mississippian inundation of North America by the Kaskaskia Sequence, Stage 2 is present in strata deposited during the regression of the Kaskaskia sea. Stage 3 was formed during the transgression and stillstand of the Absaroka Sequence and, although initially endemic, Stage 3 faunas are strongly pandemic in the end when oceanic circulation patterns were at a maximum. A mid-Leonardian sea-level drop caused the extinction of Stage 3 fauna. Sea-level rise near the end of the Leonardian and into the Guadalupian created an adaptive radiation of stentopic species of Stage 4 that quickly became extinct with the latest Permian regression.

Revision and redescription of some Lower Mississippian trilobites from the Chouteau Formation (Kinderhookian) of central Missouri

-Five genera and species of edrioasteroids co-occur in the Orchard Creek Shale (Late Ordovician, Southern Illinois) including: Savagella illinoisensis (Miller and Gurley, 1895), Hystrichopsydrax sandersi n. gen. and sp., Euhydrodiskos diktyotos n. gen. and sp., ?Isorophus sp., and ?Pyrgocystis sp. The first three listed taxa are endemic to the Orchard Creek. Savagella and Hystrichopsydrax are unusual Agelacrinitidae Chapman, 1860; Euhydrodiskos is classified within the Lebetodiscidae Bell, 1976. Skeletal features of these three taxa imply unique functional and life mode adaptations in three areas: attachment, protection, and respiration. Functional and life mode inferences are supported by paleoecologic data. Savagella and Hystrichopsydrax are unique among post-Cambrian edrioasteroids in possessing a thickened proximal peripheral rim circlet having vertical mutual articulations resulting in a rigid peripheral thecal framework. This allowed exploitation of perishable, pliant, relatively flat surfaces but presumably inhibited attachment to rigid, changing, curved surfaces such as were utilized by most post-Cambrian edrioasteroids. Hystrichopsydrax was protected by thecal plates bearing large spinose processes. Savagella and Euhydrodiskos each had camouflage protection. Euhydrodiskos has an unusually large hydropore, perhaps implying enhanced respiratory capability compared with other lebetodiscids. Orchard Creek edrioasteroids occur in a thin silty shale to limestone transitional shallow marginal marine sequence and are accompanied by a sparse but diverse invertebrate macrofauna.

PERMIAN TRILOBITES FROM WEST TEXAS

ABSTRACr--Trilobites occur in two generically distinct faunas in the Permian strata of West Texas. The stratigraphically lower fauna, composed of Ditomopyge decurtata (Gheyselinck), Ditomopyge sp., Triproetus angustus n. sp., Triproetus tumidus n. sp., Triproetus altasulcus n. sp., is present in Wolfcampian and early Leonardian strata. The stratigraphically upper fauna, present in late Leonardian and Guadalupian strata, is comprised of Delaria antiqua (Girty), Delaria granti n. sp., Delaria brevis n. sp., Delaria westexensis n. sp., Delaria chinatiensis n. sp., Novoameura vitrumons n. sp., Anisopyge perannulata (Shumard), and Anisopyge cooperi n. sp. The lower fauna originated in the late Pennsylvanian, inhabited shallow-water environments, was relatively pandemic, and is interpreted to have become extinct as a result of marine regression during the early to middle Leonardian. The endemic upper fauna originated in deep waters of the Marfa and Delaware Basins during the late Leonardian, and, concurrent with sea level rise, migrated and diversified into the shelf-margin reefs of the late Leonardian and Guadalupian. Regression during the Late Permian resulted in extinction of this second Permian trilobite fauna.

TRILOBITE ASSOCIATIONS FROM THE CHOUTEAU FORMATION (KINDERHOOKIAN) OF CENTRAL MISSOURI

Three distinct trilobite associations can be recognized in the Chouteau Formation (Tournaisian, Early Carboniferous) of central Missouri. These associations appear to be lithologically and environmentally sensitive. Association A, the stratigraphically lowest association, contains six genera and is among the most diverse Carboniferous trilobite associations known in North America. This association is dominated numerically by Proetides colemani and exhibits a restricted geographic and stratigraphic distribution. The association is found only in the basal 20 cm of the Chouteau Formation at one locality, in strata representing transgressive subtidal deposits. Association B is found within subtidal and open shelf lithologies and is dominated by two trilobite species, Breviphillipsia sampsoni and Breviphillipsia ? swallowi. Breviphillipsia sampsoni, an apparently eurytopic species, is found in both shaly and carbonate strata but is predominately recovered from the shaly partings and interbeds. Breviphillipsia ? swallowi, a more stenotopic species, occurs primarily in the more carbonate-rich intervals. In addition, five trilobite species, subordinate in numbers, are only locally common in Association B. The sparse trilobite fauna of Association C is dominated numerically by Namuropyge ? armata, and is contained within open shelf sediments that interfinger with mud biostrome lithologies. Early Carboniferous adaptive radiation of trilobites resulted from the creation of new ecospace by transgression. This allowed initially eurytopic trilobites to move into and occupy certain niches that may have been unavailable to them prior to the Frasnian extinctions. With continued deepening, niche-specialized associations developed in more offshore settings.

LOWER MISSISSIPPIAN TRILOBITES FROM SOUTHERN NEW MEXICO

Abstract Twenty-three species of trilobites are recognized in the lower Mississippian Caballero and Lake Valley Formations of southern New Mexico. Species exhibit a segregation into shelf and off-shelf faunas, and can be subdivided into three distinct stratigraphic faunas. Species found in the Caballero Formation are similar to those found in the Chouteau Formation of Missouri. A second fauna, comprising species found in the Alamogordo, Nunn, and Tierra Blanca Members of the Lake Valley Formation, is correlated with the Fern Glen and Burlington Formations of Missouri. The third fauna found in the Arcente and Dona Ana Members of the Lake Valley Formation is correlated with the Warsaw and Salem Formations of the United States midcontinent region. Named species from the Kinderhookian Caballero Formation include: Dixiphopyge armata (Vogdes, 1891), Comptonaspis swallowi (Shumard, 1855), Brachymetopus indianwellsensis new species, Ameropiltonia perplexa new species, Griffithidella caballeroensis new species, and Kollarcephalus granatai new genus and new species. Named species from the Lake Valley Formation include: Pudoproetus fernglenensis (Weller, 1909), Breviphillipsia semiteretis Hessler, 1963, Griffithidella doris (Hall 1860), Phillibole planucauda (Brezinski, 1998), Piltonia carlakertisae new species, Australosutura llanoensis Brezinski, 1998, Thigriffides triangulatus new species, Thigriffides? alamogordoensis new species, Namuropyge newmexicoensis new species, Nunnaspis stitti new genus and new species, Hesslerides arcentensis new genus and new species, as well as an unnamed species of Proetides Hessler, 1962, Namuropyge Brezinski, 1988, and Thigriffides Hessler, 1965.

Trilobites from Lower Mississippian starved basin facies of the Southern United States

A distinctive trilobite fauna occurs within condensed stratigraphic sections of the Lower Mississippian (Tournaisian) Chappel Limestone of the Llano region of Texas, the Welden Limestone of Oklahoma, and the Chouteau Limestone of Union County, Illinois. The seven species comprising this fauna are interpreted to have inhabited sediment-starved basinal environments. The starved-basin facies existed in the south-central United States throughout the Tournaisian (Kinderhookian to Osagean). Two species from this fauna, Australosutura llanoensis, and Carbonocoryphe planucauda, are new. The remaining five species, Griffithidella doris (Hall), Griffithidella alternata (Girty), Carbonocoryphe depressa (Girty), Thigiffides roundyi (Girty), and Pudoproetus chappelensis (Hessler), are restricted to starved-basin facies.

Permian trilobites from the San Andres Formation, New Mexico, and their relationship to species from the Kaibab Formation of Arizona

A new genus, Novoameura, is erected with the type species Anisopyge mckeei Cisne. Delaria macclintocki Cisne from the Kaibab Formation of Arizona is herein regarded as a junior synonym of Delaria sevilloidia (Chamberlain), which was originally described from the Phosphoria Formation of Wyoming. The Leonardian (Permian) San Andres Formation of the Sacramento Mountains, central New Mexico, contains trilobite species known both from the Kaibab Formation of Arizona and the Phosphoria Formation of Wyoming, but lacks trilobite species known from the nearby Permian of West Texas.

Phylogenetics, Systematics, Paleoecology, and Evolution of the Trilobite Genera Paladin and Kaskia from the United States

Abstract Late Mississippian and earliest Pennsylvanian trilobite faunas of North America are dominated by the Paladin and Kaskia clades. Phylogenetic analysis of middle Carboniferous species of these clades demonstrates the close ancestral relationship between these groups. The Kaskia clade consists of eight species: K. chesterensis Weller, 1936, K. osagensis (Cisne, 1967), K. longispina (Strong, 1872), K. wilsoni (Walter, 1924), K. genevievensis (Walter, 1924), K. rosei (Cisne, 1967), K. gersnai n. sp., and K. rollinsi n. sp. Kaskia Weller, 1936 ranges from late Osagean to middle Chesterian (early Visean-early Serpukhovian) and is restricted to cyclothemic shelf and nearshore deposits. Species of Kaskia appear to have evolved in areas of shallow water and high environmental stress. The Paladin clade consists of 12 species including previously named species P. morrowensis (Mather, 1915), P. girtyianus Hahn and Hahn, 1970, P. rarus Whittington, 1954, P. helmsensis Whittington, 1954, and P. moorei (Branson, 1937). New species belonging to this clade are Paladin moorefieldensis n. sp., P. pleisiomorphus n. sp., P. imoensis n. sp., P. mangeri n. sp., and P. wapanukaensis n. sp. This group ranges from the early Chesterian to early Morrowan (late Visean-late Bashkirian). Species of Paladin appear to be confined to outer shelf shelf-edge and off-shelf facies where presumably deeper water environments existed. This is manifested in their paleogeographic distribution, which is paleoenvironmentally controlled.

LOWER MISSISSIPPIAN TRILOBITE BIOSTRATIGRAPHY OF THE CENTRAL UNITED STATES, AND SOME NEW OSAGEAN SPECIES

Abstract Six stratigraphically distinct trilobite faunas are recognized in the Lower Mississippian strata of the central United States. These faunas range in age from earliest Kinderhookian to Meramecian, and are, in ascending order: Pudoproetus missouriensis, Comptonaspis swallowi, Proetides insignis-Perexigupyge, Breviphillipsia semiteretis, Exochops portlockii, and Hesslerides bufo. Trilobite species diversity waxed and waned through the early Mississippian of the central United States, but reached its maximum during the late Kinderhookian within the Comptonaspis swallowi fauna. The Comptonaspis swallowi, Breviphillipsia semiteretis, and Exochops portlockii faunas of the mid-continent can be correlated with the C. swallowi, B. semiteretis, and Hesslerides arcentensis faunas of the Caballero and Lake Valley Formations of New Mexico. The vertical distribution, composition, and diversity variations among individual faunas suggest that they are evolutionarily discrete and therefore of biostratigraphic utility. Their stratigraphic distribution appears to be controlled by sea level and climatic fluctuations. New Osagean trilobites identified and described are Exochops burlingtonensis n. sp. and Richterella carteri n. sp. from the Burlington Formation of Missouri, Australosutura osagensis n. sp. from the Keokuk Limestone of Missouri and the Arcente and Dona Ana Members of the Lake Valley Formation of New Mexico, and Spergenaspis boonensis n. sp. from the Boone Formation of Oklahoma.