Hermit crabs have left a rich fossil legacy of epi- and endobionts that bored or encrusted hermit crab-inhabited shells in specific ways. Much of this rich taphonomic record, dating from the middle Jurassic, has been overlooked. Biological criteria to recognize hermitted shells in the fossil record fall within two major categories: 1) massive encrustations, such as encrusting bryozoans; and 2) subtle, thin encrustations, borings, or etchings that surround or penetrate the aperture of the shell. Massive encrustations are localized in occurrence, whereas subtle trace fossils and body fossils are common, cosmopolitan, and stratigraphically long-ranging. Important trace fossils and body fossils associated with hermit crabs are summarized here, with additional new fossil examples from the eastern Gulf Coast. Helicotaphrichnus, a unique hermit crab-associated trace fossil, is reported from the Eocene of Mississippi, extending its stratigraphic range from the Pleistocene of North America and the Miocene of Europe.

Remarkably well-preserved specimens of Marocella Geyer, 1986, from the Lower Cambrian Shackleton Limestone of Antarctica show that although affinity with chondrophorine cnidarians is improbable, its rigid caplike shell also is unlike that of any known mollusk. Association with sclerite-bearing taxa cannot be ruled out, but at present the phylogenetic affiliation of the genus remains equivocal.

Melanosclerites are rod-shaped, pseudochitinous microfossils of problematic affinity. They have not been widely studied. The first North American discovery of melanosclerites is here reported; Melanostylus coronifer and Melanosteus acutus (the latter with two subspecies), of Devonian (Late Siegenian) age, were discovered in the Indian Cove Formation of the Upper Gaspé Limestones from the Gaspé Peninsula, Quebec, Canada.

These melanosclerites bear a strong resemblance to the modern cubomedusa polyp Carybdea alata and the planula stages of the hydrozoan Pennaria tiarella. They are interpreted as being the embryonic planula and early polyp stages of scyphozoans, cubozoans, and hydrozoans.

Consequently, Semenola semen Schallreuter, 1981, is considered an early growth stage of M. acutus anceps and thus a junior synonym; similarly, Eichbaumia incus is a junior synonym of Melanostylus coronifer; while, on the basis of their three-fold symmetry, Orthopelta? femuralis Eller, 1945, and Menola os Schallreuter, 1981, are treated as junior synonyms of Melanofurca neptuni Eisenack, 1963. Melanosclerites could represent the planula and polyp stages of any of the three classes of Cnidaria; therefore, the order Melanoscleritoitidea Eisenack, 1963, and the family Melanoscleritoitidae are here rejected because the supposed family crosses the boundaries of classes. The new subspecific combinations Melanosteus acutus acutus, M. acutus filiformis, and M. acutus anceps are proposed, their diagnoses being emended; the diagnosis of Melanostylus coronifer is also emended.

Melanosclerites appear to be strongly facies controlled and thus may have potential for paleoenvironmental and paleogeographical reconstructions.

Forty-three species of 25 genera are described in a collection of 170 large, massive reef corals from the upper Eocene Gatuncillo Formation near Lago Alahuela in central Panama. Comparisons with type material for other Eocene Caribbean reef corals suggest that 27 of these species are new. Twenty-four of these species are named herein. Like other Eocene Caribbean reef-coral faunas, the fauna is rich in Astrocoenia, Actinacis, and Astreopora; however, unlike other faunas, plocoid and meandroid members of the family Faviidae (e.g., Montastraea, Agathiphyllia, Goniastrea, and Colpophyllia) are abundant. Also present are the oldest known representatives of the genera Meandrina, Coscinaraea, Alveopora, Heliopora, and Pocillopora, as well as the only recorded occurrences of Coscinaraea and Cyathoseris from the Caribbean. Comparisons with Oligocene and Recent Caribbean reef-coral faunas suggest that the generic composition of Cenozoic Caribbean reefs became established during the Eocene. With exception of the family Mussidae, much of the post-Oligocene history of the Caribbean is one of extinction at the generic level (19 of the 28 Eocene genera became extinct) and proliferation of species within the surviving genera.

An assemblage of well-preserved octocoral holdfasts and sclerites has been collected from the Red Bluff Formation at the Chickasawhay River, Wayne County, Mississippi. Seven families were identified, utilizing a collection of approximately 1,000 sclerites. Families represented are Telestidae, Nephtheidae, Anthothelidae, Paramuriceidae, Plexauridae, Virgulariidae, and Gorgoniidae. These families, with exception of the Gorgoniidae, are here reported for the first time as fossils from the Gulf Coast region. The collection represents one of the most diverse fossil octocoral assemblages known from a single location.

Three new species of freshwater gastropods are described from the lower Eocene Adjuntas Formation. Five more species are reported from the same fauna. This is the first report of Tertiary freshwater Mollusca of the Campanian–lower Eocene Difunta Group. The three new species (Hemisinus (Longiverena) reticulosus, Hemisinus (Longiverena) adjuntaensis, and Melanatria ypresiana) belong to the family Thiaridae, which today is a worldwide distributed group of freshwater gastropods of medical importance. Paleoenvironmental interpretation for red, green, and yellow beds of Adjuntas Formation suggests delta-plain deposits. Gastropods here described lived in swamps and marshes of this portion of the ancestral Gulf of Mexico.

The remaining terrestrial gastropod fauna of the late Oligocene–early Miocene Cabbage Patch beds of western Montana is composed of nine new species, all from extant genera now occurring in the western United States: Vallonia berryi, [Succineidae] montana, Nesovitrea pulchra, Deroceras securis, D. mahiz, Punctum alveus, Polygyroidea montivaga, Oreohelix brandi, and Monadenia? n. sp. A, which is described from neanic material. All except the Monadenia? represent first occurrences of the respective genus in North America. The terrestrial fauna suggests that climatic and environmental conditions during the late Oligocene–early Miocene interval must have been very similar to those of the present. Two sizes of gastropod eggs, attributed to P. montivaga and V. berryi, were found at one locality. Monadenia? n. sp. A is of limited use, due to rarity, as an index fossil for the upper Cabbage Patch beds.

Describing the chemical ontogeny of 36 specimens of Nautilus allowed the identification, as well as the determination of the relative effects, of the controls on Mg and Sr concentration in skeletal aragonite. The previously documented trend that aragonite contains higher concentrations of Sr than Mg persists within skeletal structures of Nautilus. This relationship suggests that neither physiological nor environmental controls overwhelm the mineralogical control. Significant differences in Mg and Sr concentrations of nacreous shell, prismatic shell, and septal nacre suggest that these structures may form from extracellular fluids with differing elemental concentrations. Many specimens exhibit greater variability of Mg and Sr concentrations in juvenile portions of the skeleton than in more mature portions. This suggests that either the physiochemical system matures during ontogeny and achieves increasing control over skeletal chemistry or the organism adjusts to the new conditions and behavioral maturation stabilizes elemental concentrations by reducing stress. The decreased growth rate that Nautilus experiences as it approaches maturity does not effect Mg or Sr concentrations. Differences in combined Mg and Sr concentrations among species of Nautilus indicate that extracellular fluids that produce each skeletal structure are chemically distinct, with the exception of the fluids that produced septal aragnite of N. belauensis and N. scrobiculatus, and exemplify phyletic control of trace element concentration at the species level. Although significant chemical separation exists among species of Nautilus, sufficient variation and overlap persists in elemental concentrations to make a classification based solely on these two elements ineffective. Significant chemical differences between two sympatric species of Nautilus demonstrate that physiological systems, and not environmental variables, primarily control elemental concentrations in skeletal aragonite.

The Mississippian crinoid genus Dizygocrinus is revised, and the phylogeny is inferred. Eleven species are recognized, including D. biturbinatus (Hall), D. indianaensis (Lyon and Casseday), D. caroli (Hall), D. whitei (Wachsmuth and Springer), D. originarius (Wachsmuth and Springer), D. montgomeryensis (Worthen), D. gorbyi (Miller), D. venustus (Miller), D. peculiaris (Miller and Gurley), D. mutabilis (Wachsmuth and Springer), and D. cantonensis (Wachsmuth and Springer). Nomenclatoral revisions include recognition of D. gorbyi and D. peculiaris as valid species and designation of the following as junior synonyms: D. calvus, D. crawfordsvillensis, D. intermedius, D. mediocris, and D. somersetensis. Dizygocrinus is now recognized from both the late Osagean and Meramecian on both the eastern and western margins of the Illinois Basin.

Dizygocrinus is first recognized virtually simultaneously on both the eastern and western margins of the Illinois Basin. Migration proceeded in both directions, but was most common later in the history of the genus. The principal radiation on the western basin margin was among species with generally smooth aboral cup plates, whereas on the eastern margin sculptured species account for the principal species radiation.

The importance of hydrodynamic lift to the autecology of stalked crinoids was evaluated by comparing the maximum hydrodynamic lift experienced by the crinoid crown to the weight of the crinoid in water. Results of the analysis suggest that even under optimum conditions a current velocity of over 20 cm/s would be required to produce enough lift to overcome the animals' weight in water. This implies that under normal conditions crinoids could not function as kites, using the stalk as a tether, unless they possessed some means of reducing their densities. Lift, however, may play a role in the reorientation of crinoids in response to current direction changes, and also in elevating the crown above the substrate following dislodgement or crawling.

The unusual extant crinoid Holopus rangii d'Orbigny lacks a column, cements directly to hard substrates, has a conical to tubular dorsal cup in which plate sutures cannot be discerned, and has 10 tapered arms that are able to enroll swiftly into a “fist-like” configuration when disturbed. The first SEM study of H. rangii is presented herein. The gross morphology and skeletal microstructure of this species display many characteristics that bear an obvious relationship to the functional morphology of the living animal. Dorsal cups show a range of morphologies, reminiscent of those found in acorn barnacles and other tubular encrusters. During arm enrollment, the adjacent arms abut and form an impervious seal. Of the two specimens dissected, one had a regenerating arm.

Membranous phylloid algae of the late Paleozoic have commonly been identified as Anchicodium Johnson, whereas the genus was originally described as being cylindrical and branched, much like modern Codium. The holotypes cannot be located, but examination of one lectotype specimen and neotypic thin sections from material from several of Johnson's original collection sites indicates that the original descriptions were valid.

A new morphological type of Paleozoic calcareous alga is represented by Calcipatera cottonwoodensis n. gen. and sp., a codiacean species found in the Cottonwood Limestone Member, Lower Permian, of eastern Kansas. The new species, as reconstructed from serial sections of weathered out, in situ, intact specimens, had a broadly obconical, cup-like membranous thallus. The internal structure of the membrane as seen in cross section consisted of a medulla with mosaic sparry calcite and bilateral cortices with calcite packets forming utricular molds similar to those of other known membranous algae. The sparry calcite apparently replaced the lightly calcified or uncalcified intercoenocytic spaces in the medulla and the calcite crystals replaced the interutricular aragonite. The organism had previously been identified as Anchicodium Johnson.

As Torres (1991) and others have noted, the term “algae” no longer refers to a taxonomically useful group. It does, though, refer to an easily recognized adaptive facies. This adaptive facies contains both prokaryotes and eukaryotes, as do various others (e.g., nanoplankton or decomposers). The blue-green algae are thus indeed algae in this useful sense. More than terminology is involved, because a concept like that of adaptive facies can be forgotten if we focus solely on taxa. The terms “proalgae” and “eualgae” can be used transparently when we want to distinguish prokaryotic from eukaryotic algae. “Proalgae” has in fact been proposed as a formal taxon (Van Valen, 1986); the terms come from Van Valen and Maiorana (1980). Similarly, one can refer to the nonhomologous kinds of flagellae as proflagellae and euflagellae while retaining a general term.

Species of Baculites are important marker fossils in the Upper Cretaceous rocks of the Western Interior of the United States and provide indices for 20 of the 29 Campanian and Maastrichtian zones recognized by Cobban (in Gill and Cobban, 1966; Cobban, 1977). They often occur in rock-forming proportions (Gill and Cobban, 1966, Pl. 11, fig. 3) and are common up through the lower Maastrichtian Baculites clinolobatus zone. In the type area of the Fox Hills Formation in west-central South Dakota, B. clinolobatus is present in the lower part of the Mobridge Member of the Pierre Shale, but Baculites are rare or absent in the rest of the member as well as in the overlying Elk Butte Member that forms the uppermost part of the Pierre Shale (Waage, 1968, p. 50, 51, fig. 6). Only the diminutive Baculites columna Morton, 1834, has been noted from the succeeding Fox Hills Formation (Waage, 1968). The highest marine Cretaceous rocks of the Western Interior are characterized instead by Sphenodiscus and a range of scaphitid species (Hoploscaphites, Discoscaphites). It is therefore of some interest to describe, for the first time, the baculitids from the very high Cretaceous of the Western Interior. The material described below was collected from the Fox Hills Formation by N. L. Larson, P. L. Larson, and R. A. Farrar of the Black Hills Institute of Geological Research, Hill City, South Dakota. We are grateful to them for allowing us to describe this interesting collection. Specimens cited below are deposited in the collections of the Black Hills Institute (BHI) and in the U.S. National Museum of Natural History (USNM) in Washington, D.C.

In 1968, R. H. Kilpatrick of Milton, Florida, discovered three large entelodont teeth in the bed of the Conecuh River in Alabama. Frank C. Whitmore, Jr. of the U.S. Geological Survey identified the specimens, visited the fossil locality, and began a study of this unique find. Two decades later, Whitmore realized that devotion to his true research interest, the study of fossil cetaceans, would not allow him time to complete the study of the entelodont remains. He generously passed the specimens on to the writer to finish the project for which he had laid the groundwork.

Certain groups of living Chlorophyta (green algae) have thalli made up of long, tubular cells with many nuclei and many plastids (Tappan, 1980; Bold and Wynne, 1985). The only cross walls in these coenocytes are those that isolate the gamete-producing structures. As the coenocytes approach the edges of the thallus, they branch, generally dichotomously, one or more times and eventually terminate in clavate or bulbous segments called utricles (Latin for small bag or bottle). Thus, the utricles are the termini of coenocytes that occur along the surface of the thallus and interface with the environment. Utricles have been figured in many descriptions and illustrations of such calcified genera as Halimeda (Wray, 1977) and such noncalcareous genera as Codium (Bold and Wynne, 1985). Because of the easily recognized distinction between the parts of the coenocytes, the thallus in cross section consists of a cortex occupied by the utricles and their contiguous segments and a medulla occupied by the long tubular portions of the cell (Figure 1).

A considerable part of micropaleontological work consists of picking microfossils for various types of analyses. Physical removal of specimens from a sample is necessary, for example, in morphometric, stable isotope, geochemical, and molecular studies of microfossils. The traditional method for picking microfossils involves transfer of each specimen from the picking tray to a slide using a moistened brush or a needle. This process requires a great deal of time and the risk of losing or damaging the specimen on the way from the picking tray to the slide is apparent. Furthermore, in geochemical analyses, the use of a moistened brush or needle for picking considerably increases the risk of contamination by undesirable organic substances, such as amino acids and polysaccharids. The brush-licking practised by some micropaleontologists results in anthropogenic contamination, which affects the results of molecular micropaleontologic analyses. We present a simple and effective device for microfossil picking, which may save about 60 percent of the time devoted to picking microfossils and prevent contamination during preparation.

In the November 1990 (Vol. 64, no. 6) issue of the Journal of Paleontology, Lehman and Carpenter described an Aublysodon, which at the time was believed to be the most complete Carnosaur known from the Upper Cretaceous Kirtland Shale of northwestern New Mexico. Recently, a more complete specimen, considered to be a tyrannosaurid dinosaur on the basis of a proximally constricted third metatarsal and a partial D-shaped (in cross section) premaxillary tooth (Molnar, 1990), has been brought to the attention of the Museum of Geology at Arizona State University by an amateur paleontologist who recognized its scientific importance after obtaining it from an individual in New Mexico. The remains of this dinosaur, collected in northwestern New Mexico sometime in late 1989 or early 1990 by unknown persons, include both cranial and skeletal material (Figure 1.1).

The trilobite Phacops rana var. milleri Stewart, 1927, was based on five specimens collected from the Silica Shale (Middle Devonian) in a quarry formerly owned by the Sandusky Cement Company, near Silica, Lucas County, Ohio. The “cotypes” (=syntypes of modern terminology) were catalogued as number 16266 in the Orton Geological Museum of The Ohio State University. Study of specimens in the OSU collection reveal four extant syntypes belonging to two subspecies of Phacops rana (Green, 1832). Three complete specimens and one separate eye are represented. A cephalon mentioned by Stewart (1927, p. 59) is missing and presumed lost. Of the extant specimens, three belong to P. rana milleri and one belongs to P. rana crassituberculata Stumm, 1953.