Thomas A. Stidham

Dietary controls on extinction versus survival among avian megafauna in the late Pleistocene

The late Pleistocene extinction decimated terrestrial megafaunal communities in North America, but did not affect marine mammal populations. In coastal regions, marine megafauna may have provided a buffer that allowed some large predators or scavengers, such as California condors (Gymnogyps californianus), to survive into the Holocene. To track the influence of marine resources on avifaunas we analyzed the carbon, nitrogen, and hydrogen isotope composition of collagen from late Pleistocene vultures and raptors, including species that survived the extinction (condor, bald eagle, golden eagle) and extinct species (teratorn, black vulture). At the Rancho La Brea and McKittrick tar pits of southern California, isotope values for extinct teratorns (Teratornis merriami ,n 10) and black vultures (Coragyps occidentalis ,n 8) show that they fed entirely in a terrestrial C3 ecosystem. In contrast, La Brea condors cluster into two groups, one with a terrestrial diet (n 4), and the other with a strong marine influence (n 5). At localities in the American southwest, Texas, and Florida, where condors became extinct, they have isotope values indicating entirely terrestrial diets (n 10). Our results suggest that dependence upon terrestrial megafaunal carrion as a food source led to the extinction of inland California condor populations and coastal populations of teratorns and black vultures at the Pleistocene-Holocene boundary, whereas use of marine foods allowed coastal condor populations to survive.

Morphology of the quadrate in the Eocene anseriform Presbyornis and extant galloanserine birds.

Despite the notoriety, phylogenetic significance, and large number of available specimens of Presbyornis, its cranial anatomy has never been studied in detail, and its quadrate has been partly misinterpreted. We studied five quadrates of Presbyornis that reveal features hitherto unknown in the anseriforms but otherwise present in galliforms. As a result, we analyzed the variable quadrate characters among all extant galloanserine families and identified synapomorphies and other morphological variation among the major galloanserine clades. In terms of quadrate morphology, Presbyornis is more plesiomorphic than any extant anseriform (including the Anhimidae) and shares ancestral galloanserine characters with the Megapodiidae, the earliest branch of extant galliforms. The quadrates morphology is inconsistent with the currently accepted anseriform phylogeny that nests Presbyornis within the crown‐group as a close relative of the Anatidae. The presbyornithid quadrates exhibit an unusual variation in the presence of a caudomedial pneumatic foramen, which we interpret as a result of a discontinuous change in the growth path of the pneumatic diverticulum. Another episode of morphogenetic imbalance in the growth path of the pneumatic diverticulum may have accompanied the disappearance of the basiorbital pneumatic foramen (along with the pneumatization of the pterygoid) at the origin of the crown‐group anseriforms. This episode is marked by the striking individual variation in the presence and location of pneumatic foramina in the mandibular part of the quadrate in the Anhimidae. J. Morphol., 2010.

A Galloanserine Quadrate from the Late Cretaceous Lance Formation of Wyoming

ABSTRACT. Although the monophyly and Cretaceous origins of galloanserines have been established beyond a reasonable doubt, no stem galloanserine has ever been identified and very few fossils help to date the early phylogeny of the clade. We describe a very late Cretaceous quadrate that was previously assigned to Cimolopteryx, a charadriiform genus, and identify it instead as galloanserine and probably stem anseriform. In addition to the presence of a distinctive galloanserine character complex, the quadrate shows a predominance of plesiomorphic characters that are widespread among the Neornithes and shared by Presbyornis and primitive galliforms, in particular the megapodiids. Only one character, the unique configuration of the mandibular condyle, is known only in the anseriforms and thus indicates that the quadrate most likely belongs to a stem anseriform. The bone comes from a bird that compares in size to the smallest living galliforms, which suggests that early anseriforms, and possibly all galloanserines, were small. Their size may be responsible for the paucity of their Cretaceous record and, thus, its incongruence with the molecular dating of the anseriform-galliform divergence.

Regional-scale spatial heterogeneity in the late Paleocene paratropical forests of the U.S. Gulf Coast

Abstract The study of spatial patterns in biotic compositional variability in deep time is key to understanding the macroecological response of species assemblages to global change. Globally warm climatic phases are marked by the expansion of megathermal climates into currently extra-tropical areas. However, there is currently little information on whether vegetation in these “paratropical” regions resembled spatially modern tropical or extra-tropical biomes. In this paper we explore spatial heterogeneity in extra-tropical megathermal vegetation, using sporomorph (pollen and spore) data from the late Paleocene Calvert Bluff and Tuscahoma Formations of the formerly paratropical U.S. Gulf Coast (Texas, Mississippi, and Alabama). The data set comprises 139 sporomorph taxa recorded from 56 samples. Additive diversity partitioning, nonmetric multidimensional scaling, and cluster analysis show compositional heterogeneity both spatially and lithologically within the U.S. Gulf Coastal Plain (GCP) microflora. We then use sporomorph data from Holocene lake cores to compare spatial patterns in the late Paleocene GCP with modern tropical and extra-tropical biomes. Distance decay analysis of the Holocene data reveals a higher rate of spatial turnover in tropical versus extra-tropical vegetation types, consistent with a latitudinal gradient in floral compositional heterogeneity. The specific combination of rate and scale dependency of distance decay in the Holocene assemblages prevented us from associating the late Paleocene GCP with any particular modern biome. Our results demonstrate the importance of spatial scale, taphonomy, and lithology in determining patterns of spatial heterogeneity, and show the potential of the fossil sporomorph record for studying spatial patterns and processes in deep time.

Bull Nettle (Cnidoscolus texanus) as Enemy Free Space for Orthopterans in Texas, U.S.A

Orthopterans use a wide variety of mechanisms in order to avoid and deter predators. They ingest toxic chemicals to become distasteful or toxic (Sword 1999), utilize camouflage (Belwood 1990, Nickle and Castner 1995), excrete toxic or distasteful chemicals (Idowu and Modder 1998), and utilize antipredatory spines and behaviors (Nickle and Castner 1995), all to avoid becoming a meal. Orthopterans also occupy certain toxic or spiny plants in order to reduce the chance of predation. Enemy-free space is the concept that there are methods species use to reduce or eliminate the effect of their natural enemies (Jeffries and Lawyon, 1984) such as occupation of a hole in the ground or a toxic plant. It is an old concept that can be applied broadly to many aspects of the environment and an organism’s behavior (Fryer, 1986). We have observed orthopterans use a particular plant, bull nettle (also called spurge nettle), as enemy-free space. These are initial observations and suggest further research into the association of orthopterans and this species of plant. We have made field observations of orthopteran use of Cnidoscolus texanus (Müll. Arg.) Small (bull nettle) in spring and summer for several years south of San Antonio, Bexar County, Texas, and near Buffalo, Leon County, Texas. There are many potential predators of orthopterans that occupy the sandy areas where bull nettle is common, including a wide variety of birds (including woodpeckers, flycatchers, and warblers) and lizards (including Cnemidophorus sexlineatus, Holbrookia maculata, and Cophosaurus texanus). It was after years of observation that we came to see the apparent choice of this particular plant as a refuge. We subsequently took notes on what species utilize this spiny plant. Cnidoscolus texanus is a member of the Euphorbiaceae and is common to sandy soils through much of Texas, Oklahoma, Louisiana, and adjacent Mexico (Pollard 1986). It grows to approximately 50 to 60 cm in height, has white flowers, and is covered with thin, stinging trichomes, 3 to 8 mm in length on the stems, fruits, and leaves (Pollard 1986). The trichomes contain serotonin and possibly other toxins (Lookadoo and Pollard 1991) that can cause allergic reactions and significant swelling in people. Internally, bull nettle has a latex which may contain the toxins b-amyrin, linamarin, and flavonol glycosides (Seigler and Bloomfield 1969, Kalterman and Brekon 1982). These trichomes and toxins 102 ENTOMOLOGICAL NEWS

NEW RECORDS OF RHAMMATOCERUS VIATORIUS (ORTHOPTERA: ACRIDIDAE: GOMPHOCERINAE) FROM TEXAS, U.S.A

The grasshopper Rhammatocerus viatorius (Saussure) occurs from South America northward to the southwestern United States (Otte 1981). In the United States, it occurs in south central Arizona, and there are two specimens collected in 1930 and 1931 from the Chinati Mountains in Presidio County (Figure 1) in Trans-Pecos Texas (Tinkham 1948). These are the only records of this species known from Texas. On 1 July 2005, the authors collected an adult male and an adult female Rhammatocerus viatorius on a rocky hillside with tall grass (60-80 cm in height) on route 118 northwest of the McDonald Observatory, north of Ft. Davis in the Davis Mountains, Jeff Davis County, Texas (Figure 1). The locality is approximately 2000 m (6500 ft) in elevation. Other grasshoppers observed at the locality with Rhammatocerus were Melanoplus lakinus, Melanoplus aridus, Opeia obscura, Dactylotum bicolor variegatum, Mermeria texana, and Eritettix tricarinatus. These are the first records of R. viatorius in over 70 years from Texas and are a northeastern range extension of that species’ occurrence in Texas by approximately 100 km (65 miles). The Chinati and Davis Mountains are not connected mountain ranges and have intervening desert. Thus, these individuals may be from an isolated population separate from those in the Chinati Mountains or they may be recent dispersers to Jeff Davis County. These new specimens will be placed in Texas A&M University Insect Collection (Department of Entomology, Texas A&M University). The occurrence of adults in the Davis Mountains in early July differs from reports of adults in the late spring in Arizona and the Chinati Mountains (Otte 1981). However, the morphology of the specimens is consistent with previously described specimens, having red hind tibiae, six to eight large black spots on the tegmen, and angular bands on the outer face of the hind femora. In addition, the sulci on the pronotum match those illustrated by Otte (1981), and the male specimen’s phallus and epiphallus do not differ from those illustrated for specimens from Mexico (de Assis-Pujol 1998). Additional collections are necessary to determine if these individuals are late survivors from the previous spring or if the Davis Mountains individuals occur at a different time of year. Volume 118, Number 3, May and June 2007 317

New observations of host plant usage by Clematodes larreae (Orthoptera: Acrididae: Copiocerinae), including a new host plant in Texas, U.S.A

Clematodes larreae Scudder is a small flightless gray grasshopper that occurs in the western part of Texas, southern New Mexico, and adjacent Mexico (Rehn and Eades 1961). The type material was collected on Larrea (creosote bush), and the grasshopper’s specific epithet is in reference to that host plant (Scudder 1900). Clematodes larreae is predominantly found on Larrea (Rehn and Eades 1961, Tinkham 1948), but it also has been recorded on low grasses (Poaceae), Koeberlinia spinosa (Koeberliniaceae, crucifixion thorn), Fallugia paradoxa (apache plume, Rosaceae), Macrorhamnus (Colubrina) ericoides (Rhamnaceae, snakewood), and Acacia spp. (Fabaceae) (Rehn and Eades 1961). On 25 June 1983 and 30 June 2005, we collected specimens and observed other C. larreae on Prosopsis glandulosa (Fabaceae, honey mesquite) in TransPecos Texas. These specimens will be placed in the Texas A & M University Insect Collection (Department of Entomology, Texas A&M University). The occurrence of C. larreae on mesquite previously has not been reported. We collected one male and three female specimens in 1983 approximately 40 miles east of El Paso on Interstate 10, El Paso County, Texas, and three males and three females in 2005 west of Fort Hancock on Interstate 10, Hudspeth County. At both locations, the soil is light-colored sand, and the vegetation is composed of a mixture mostly of mesquite and creosote. At the Ft. Hancock locality, individuals were observed on both mesquite and creosote. During the time we were at the Ft. Hancock locality in the mid-afternoon, it was extremely hot (over 43°C) and we observed that insects died within seconds if they came into contact with the sandy surface of the ground. The Clematodes individuals that occurred on mesquite were easily located. They appeared to occupy the highest, visually exposed positions on the center tallest branches of individual mesquite trees (sometimes over two meters tall) in a cluster of three or more mesquite trees. We believe that this position was taken in order to keep away from the extremely hot ground surface. In 1983, we only encountered Clematodes by beating low vegetated branches of mesquite where the specimens were always well hidden. The temperature was not as extreme at that time. Volume 118, Number 2, March and April 2007 207