Young Species Research Articles

Ontogeny, functional morphology, and comparative morphology of lower (Stage 4) and basal middle (Stage 5) Cambrian gogiids, Guizhou Province, China

Three gogiid eocrinoids, numbering in the thousands of specimens, are well known from the lower Cambrian (Stage 4) Balang Formation (Guizhoueocrinus yui) and basal middle Cambrian (Stage 5) Kaili Formation (Kaili Biota) (Sinoeocrinus lui and Globoeocrinus globulus) that resided on the Yangtze-South China Plate (modern Guizhou Province, China). In each species a complete ontogenetic sequence, using thecal height (TH) as a scale, juvenile stage (early, middle, and late substages), mature stage (early, middle, and late substages), and a gerontic stage can be identified. Sutural pores appeared in an orderly sequence; below the ambulacrals, above the stalk and generally over the theca, in that order. In younger species their emplacement and growth was commonly precocious relative to G. yui. Also, their shape ranges from circular to oval to triangular in a single growth sequence, after the establishment of the 2-1-2 pattern; brachioles were added in series of five and were also precocious in time of occurrence in younger species. Thecae in younger species tend to retain juvenile aspects relative to G. yui. All of these species lived in outer shelf settings in fine-grained, organic-rich siliciclastics.

The shallow marine placodont Cyamodus of the central European Germanic Basin: its evolution, paleobiogeography and paleoecology

The oldest record of Cyamodus is a skull of Cyamodus tarnowitzensis (Gürich 1884, Zt dt Geol Ges. 36:125–144) from Pelsonian shallow marine deposits. During the middle Illyrian, placodonts disappeared from the Germanic Basin. With renewed upper Illyrian transgression, Cyamodus rostratus (Münster 1839, Über einige ausgezeichnete fossile Fischzähne aus dem Muschelkalk bei Bayreuth. Birner, Bayreuth, p. 14) appeared which was found in terebratulid shell-rich shallow marine deposits. Abundant remains of Cyamodus muensteri (Agassiz 1839), traditionally referred to as Cyamodus hildegardis and here synonymised with C. muensteri, have been reported from the upper Illyrian/middle Fassanian. Skeletal remains of this species are from the Grenzbitumenzone of the Monte San Giorgio lagoons. The youngest species, Cyamodus kuhnschnyderi (Nosotti and Pinna 1993, Compt Rend Acad Sci Paris. 317:847–850), has been found in the upper Fassanian/lower Longobardian of the southern Germanic Basin or Burgundian Gate when marine facies in the Germanic Basin had nearly disappeared. These successive species provide evidence of monophylogenetic development with a trend towards anterior upper and lower jaw teeth reduction, along with a shortening of the rostrum, over an interval of five million years (243–238 Ma). This evolutionary trend most probably reflects adaptation to specialised feeding on seaplants. The Cyamodus osteoderm carapace was not fused to the vertebral column, and appears to have been primarily a body enhancement that produced neutral or negative buoyancy to facilitate long-period diving.

Late Moscovian (Carboniferous) conodonts of the genus Swadelina from the Donets Basin, Ukraine

Troughed conodonts of the late Desmoinesian genus Swadelina are common in the C2-7(M) Suite (upper Moscovian, middle Pennsylvanian) in the Donets Basin, Ukraine. The youngest species, Swadelina sp. 1, is very similar to Swadelina nodocarinata (Jones). It was found for the first time in the uppermost part of theC2-7(M) Suite in the Gurkova Valley section. Two older troughed late Moscovian (early Desmoinesian) species, known as Streptognathodus dissectus Kossenko and S. concinnus Kossenko, are herein assigned to Swadelina on the basis of their similarities to this genus. Theymay have given rise to the American Desmoinesian Sw. nodocarinata and Sw. neoshoensis Lambert, Heckel andBarrick via Swadelina sp. 1. Swadelina probably appeared earlier inMoscovian time in eastern Europe than in North America.

Trigonotarbid arachnids from the Lower Devonian (Lower Emsian) of Alken an der Mosel (Rhineland-Palatinate, SW Germany)

New material of the trigonotarbids Alkenia and Archaeomartus from the Lower Devonian type locality Alken an der Mosel/Germany is described. Stormer’s original description of Alkenia is essentially confirmed and supplemented. The genus is placed in Aphantomartidae. In contrast to earlier accounts, we show that Archaeomartus has an anterior diplotergite and a longitudinally three-divided posteriormost (ninth) tergite. The new family Archaeomartidae is proposed. Whether a marginal row of larger tubercles on the opisthosoma can be recognized is strongly influenced by the taphonomic history of the fossil, and sexual dimorphism may also be involved. Thus, we propose that Archaeomartus levis and A. tuberculatus, which can be discriminated solely by the presence or absence of this feature, are synonyms. Furthermore, morphological similarity suggests the possibility that archaeomartids, with their opisthosomal tergites divided into three plates, gave rise to the later (Carboniferous) anthracomartids, specifically through the division of the lateral plates and the ninth tergite. Finally, our reassessment of Archaeomartus shows that ‘A.’ roessleri Dunlop and Brauckmann, 2006 can no longer be adequately maintained in this genus. This younger species from the early Upper Carboniferous of Hagen-Vorhalle, Germany, is reassigned to Namurotarbus n. gen. as Namurotarbus roessleri n. comb.

Phylogeny, divergence-time estimation, biogeography and social parasite–host relationships of the Holarctic ant genus Myrmica (Hymenoptera: Formicidae)

We reconstructed a molecular phylogeny of the ant genus Myrmica, tested reciprocal monophyly of the Nearctic and Palearctic representatives, and inferred social parasite–host relationships for five workerless inquilines and four temporary parasites . We sequenced six gene fragments of 106 specimens (17 not identified to species), analysed the data with Bayesian phylogenetic inference and maximum likelihood, and estimated divergence times using penalized likelihood. Our well resolved phylogeny supported most morphologically defined species groups. The Nearctic and Palearctic species were not reciprocally monophyletic, which suggested repeated species interchange across the Beringian land bridge. Parasitism evolved several times in Myrmica. Three inquilines and one temporary parasite were closest relatives of their host, two inquiline species and one temporary parasite clustered basally to their host(s), and two temporary parasites more distantly. Myrmica probably diversified following drastic climatic cooling at the Eocene–Oligocene boundary ca. 34 Ma, the oldest species groups being rugosa and ritae in central and southeastern Asia. The oldest inquiline, Myrmica karavajevi, was estimated at 17 Ma, the youngest species M. hirsuta at 0.8 Ma, whereas the microgyne of M. rubra is an intraspecific inquiline.

Karyotype evolution and speciation of European lilies from Lilium sect. Liriotypus

AbstractThe main purpose of this study was to clarify the speciation and taxonomic status of European representatives of Lilium sect. Liriotypus (Lilium albanicum, L. bosniacum, L. bulbiferum, L. candidum, L. carniolicum, L. chalcedonicum, L. jankae, L. pomponium, L. rhodopaeum, L. pyrenaicum) based on karyotype differentiation. Clear interspecific differentiation was revealed among karyotypes of these taxa using fluorochrome (chromomycin and DAPI) bandings, fluorescent in situ hybridization and silver staining. Differences were evident in the number and position of CMA and DAPI bands and in the number, position and activity of 18S‐26S and 5S rDNA genes. It is hypothesized that the type species of Lilium sect. Liriotypus, L. candidum, represents the ancestral species from which three evolutionary directions diverged: the first towards L. chalcedonicum, the second towards L. rhodopaeum, and the third towards L. albanicum. The radiation process expanded from L. albanicum, beyond the southeast to the central Dinaric Alps where L. bosniacum is strongly represented. Furthermore, L. carniolicum evolved from northwestern populations of L. bosniacum. According to this evolutionary hypothesis, L. pomponium and L. pyrenaicum would be the youngest species.

Evolutionary Time for Dispersal Limits the Extent but Not the Occupancy of Species’ Potential Ranges in the Tropical Plant GenusPsychotria(Rubiaceae)

Explaining the diversity in geographic range sizes among species is a central goal of ecological and evolutionary studies. We tested species age as an explanation of range size variation within a group of understory shrubs in the Neotropics (Psychotria subgenus Psychotria, Rubiaceae). We distinguish between range occupancy (filling an occupied area) and range extent (maximum distances dispersed). We used Bayesian relaxed-clock dating of molecular sequence data to estimate the relative age of species, and we used species distribution modeling to predict species' potential ranges. If the range sizes of species are limited by time for dispersal, we hypothesize that older species should have (1) larger realized range occupancies and realized range extents than younger species, (2) filled a greater proportion of their potential range occupancies, and (3) colonized a greater proportion of their potential range extents. We found (1) a significant but weak positive relationship between species age versus both realized range occupancy and realized range extent, (2) no relationship between species age and filling of potential range occupancies, but (3) that older species had colonized a significantly greater proportion of their potential range extents than younger species. Our results indicate that a time-for-dispersal effect can limit the extent of ranges of species but not necessarily their occupancies.

Why youth is not wasted on the young: immaturity in human development

Preface. Acknowledgments. Chapter 1: The Benefits of Youth. Rushing through Childhood. Views of Development. A Darwinian Perspective. I Come Not to Praise Immaturity. Chapter 2: The Youngest Species. A Brief Look at Human Evolution. The Evolution of Childhood. Timing is Everything. The Youngest Species. Chapter 3: The Slow Rate of Growing Up. The Gamble of Delayed Development. Big Brains, Social Complexity, and Slow Development. Cooperating and Competing. Family Matters. Slow Growth and Brain Plasticity. Developmental Plasticity and Evolution. When Slow is Fast Enough. Chapter 4: Adapting to the Niche of Childhood. The Benefits of Limitations. See Things My Way. Learning Language. How Do Adults View Children's Immature Thinking?. Adapting to Childhood. Chapter 5: The Advantages of Thinking You're Better than You Are. The Development of Metacognition - Knowing What We Know. Some Benefits of Less-Than-Perfect Metacognition. When We Deal with Children. Know Thyself, But Not Too Well. Chapter 6: Play: The Royal Road through Childhood. What is Play?. The Adaptive Value of Play. Children Playing, Children Learning. Play it Again, Kid. Chapter 7: The Most Educable of Animals. The Myth of Earlier is Better. Prenatal Learning. Early (Postnatal) Learning. Developmentally Appropriate Practices in Early Education. Stress in the Schoolhouse. Old Brain, New Curriculum. Chapter 8: The Changing Face of Childhood. Pushing Children through Childhood. A Brief History of Childhood. The Costs of Ignoring Immaturity: The Well-being of America's Children. The Independent Human Juvenile: A New View of Childhood?. Racing to Adulthood, Prolonging Adolescence. Epilogue: Homo Juvenalis. Revisiting Childhood. Visiting Adulthood. Notes. References. Index

New Middle Devonian trilobites from Vireux-Molhain (Ardennes, northern France)

Lower Eifelian (Middle Devonian) strata cropping out in the vicinity of Vireux-Molhain, Ardennes, France, have yielded a rich trilobite fauna. Four trilobite species are recorded, namelyCeratarges cognatus n. sp.,Rhenocynproetus catervus n. sp.,Cyphaspis n. sp. A andThysanopeltella (Septimopeltis) magnispina (Maillieux 1938).Ceratarges cognatus n. sp. is regarded as a possible transitional form betweenCeratarges faouensisMorzadec 1969 from the Massif armoricain and stratigraphically younger species from the Rhenohercynian.

Interspecific Hybridization of Fragaria vesca subspecies with F. nilgerrensis, F. nubicola, F. pentaphylla, and F. viridis

The potential of using Fragaria vesca L. as a bridge species for interspecific hybridization to F. nilgerrensis Schlect, F. nubicola Lindl., F. pentaphylla Losinsk, and F. viridis Duch. was investigated using a wide germplasm base of 40 F. vesca accessions. This study was successful in producing many hybrids between F. vesca and other diploid species indicating its value as a bridge species. Of the species used as males, F. nubicola, F. pentaphylla, and F. viridis accessions were more successful, averaging 8 to 16 fruit and 16 to 25 seeds/fruit. It was most difficult to obtain hybrids with F. nilgerrensis, which had only three seeds per fruit. Differences among pollen donors were minimal when hybrid seeds were germinated in vitro. For different species combinations, 75% to 99% of seeds had embryos and 77% to 89% of these embryos germinated. The lack of significant differences in crossability variables among the four F. vesca subspecies [i.e., ssp. americana (Porter) Staudt, ssp. bracteata (Heller) Staudt, ssp. vesca L., and ssp. vesca var. semper-florens L.] demonstrated the similarity between these species and the strong potential for gene flow between F. vesca and other diploid species. As European and North American F. vesca subspecies are not sufficiently divergent to differ in interspecific hybridization, F. vesca may be a younger species rather than an older progenitor species.

Rhythmic arm movement is not discrete.

Rhythmic movements, such as walking, chewing or scratching, are phylogenetically old motor behaviors found in many organisms, ranging from insects to primates. In contrast, discrete movements, such as reaching, grasping or kicking, are behaviors that have reached sophistication primarily in younger species, particularly primates. Neurophysiological and computational research on arm motor control has focused almost exclusively on discrete movements, essentially assuming similar neural circuitry for rhythmic tasks. In contrast, many behavioral studies have focused on rhythmic models, subsuming discrete movement as a special case. Here, using a human functional neuroimaging experiment, we show that in addition to areas activated in rhythmic movement, discrete movement involves several higher cortical planning areas, even when both movement conditions are confined to the same single wrist joint. These results provide neuroscientific evidence that rhythmic arm movement cannot be part of a more general discrete movement system and may require separate neurophysiological and theoretical treatment.

The evolution of feeding adaptations of the aquatic sloth Thalassocnus

ABSTRACT The aquatic sloth Thalassocnus is represented by five species that lived along the coast of Peru from the late Miocene through the late Pliocene. A detailed comparison of the cranial and mandibular anatomy of these species indicates different feeding adaptations. The three older species of Thalassocnus (T. antiquus, T. natans, and T. littoralis) were probably partial grazers (intermediate or mixed feeders) and the transverse component of mandibular movement was very minor, if any. They were probably feeding partially on stranded sea weeds or sea grasses, or in very shallow waters (less than 1 m) as indicated by the abundant dental striae of their molariform teeth created by ingestion of sand. The two younger species (T. carolomartini and T. yaucensis) were more specialized grazers than the three older species and had a distinct transverse component in their mandibular movement. Their teeth almost totally lack dental striae. These two species were probably feeding exclusively in the water at a greater depth than the older species.

Significance of new species of Cryptorhynchia (Brachiopoda) from the Middle Jurassic of Kutch, India

Cryptorhynchia is a brachiopod genus, until recently known only from the late Bathonian. Two new species C. karuna and C. jhooraensis are here described from the middle Bathonian at Kutch, western India and record the earliest known occurrences of the genus. They constitute ancestor-descendant lineages with the two existing younger species C. pulcherrima and C. rugosa respectively. Evolution in both cases shows ‘parallel’ trends and the descendants are scaled-down versions of their respective progenitors. Statistical analyses reveal that this evolutionary miniaturization involves allometry-induced heterochrony, especially progenesis, and is marked by a rapid speciation event compatible with the punctuational model. Evolution appears to be anagenetic and may be attributed to the unstable nature of environment where onshore innovation produced smaller descendants that adopted r-strategy. Facies distribution and functional morphology suggest that species of Cryptorhynchia were well adapted to shallow, unstable carbonate shelf. However, they disappeared suddenly at the Bathonian - Callovian boundary which was marked by a global transgression. The possible causal factors of their extinction may be the consequent changes in bathymetry and substrate condition.

Revision of the Silurian and Early Devonian chonetoidean brachiopods of southeastern Australia

Thirty-eight species of ostensibly chonetoid brachiopods (some under open nomenclature) have been described from the Silurian and Lower Devonian rocks of southeastern Australia, although most are neither widely distributed nor abundant. Descriptions of many have been based on inadequate material, and in one significant case ( Johnsonetes australis) the original material is lost, necessitating selection of a neotype to resolve formally the identity of that species in comparison with the similar species J. culleni. In this systematic revision the known species are redescribed and where possible their generic positions and possible synonymy determined; three are rejected from the Chonetoidea. Silurian taxa include melbournensis, kemezysi n.sp. and Protochonetes cf. minimus. Early Devonian faunas are much more diverse. Lochkovian species are S.? savagei n.sp., S.? psiloplia, S. cresswelli, Parachonetes robustus, and the poorly known ruddockensis. Strophochonetes cresswelli and P. are also found in the Pragian, along with Asymmetrochonetes? planata, Parachonetes baragwanathi, P.? bowieae, P.? suavis, Septachonetes micrus, taggertyensis and foedus. The youngest species in the region are Emsian: Johnsonetes australis, J. culleni, J. latus, Septachonetes melanus, Parachonetes buchanensis, P. spooneri, P. konincki and P. flemingi. No species is currently known to be sufficiently widely distributed geographically and sufficiently restricted stratigraphically to be of clear biostratigraphic use. Several former species are junior synonyms. melbournensis includes Chonetes infantilis, and Johnsonetes australis includes Chonetes teicherti. Parachonetes robustus, the name- bearer for Gill's robustus gens, certainly includes both Chonetes killarensis and C. productoida. It is likely that the two other species of this group, P. baragwanathi and P. buchanensis, are also synonymous but, for lack of appropriate specimens, this cannot be conclusively established. The Cambrian Chonetes concinna, subsequently (and wrongly) referred to Eoorthis, is refigured and confirmed as not being a chonetoidean. Chonetes gaskini is shown to be the ventral valve of a spiriferid, and Chonetes bipartita has already been assigned to the sowerbyelloid Plectodonta.

The sonniniid ammonite Euhoploceras from the Middle Jurassic of south‐west England and southern Spain

A biostratigraphical and taxonomic revision of the genus Euhoploceras is presented using new material collected from the Upper Aalenian–Lower Bajocian of south‐west England and the Betic Cordillera (Spain). Euhoploceras is shown to range from the uppermost Aalenian (Concavum Zone, Limitatum Subzone) to the Lower Bajocian (Laeviuscula Zone). S. S. Buckman's 69 species of Sonninia are grouped into three macroconch morphospecies: Euhoploceras acanthodes (Buckman), strongly ornamented, with tubercles and strong ribs throughout ontogeny; Euhoploceras marginatum (Buckman) with tuberculate inner whorls and relatively strong ribs persisting to the outer whorls, and Euhoploceras modestum (Buckman) with ribbed, sometimes slightly tuberculate inner whorls, becoming smooth or only slightly ornamented in later stages of coiling. Euhoploceras adicrum (Waagen) is a younger species with a type horizon in the Laeviuscula Zone. Dimorphism and possible polymorphism are present in both English and Spanish faunas. Euhoploceras subspinosum (Buckman) probably represents dwarf forms of E. acanthodes[M] and is included as a junior synonym of the latter; likewise, E. subdecoratum (Buckman) may belong with E. marginatum[M], although they are described separately herein. Some of the microconchs of Euhoploceras[M] are probably represented by Nannoceras. Similarities between English and Betic Euhoploceras confirm that during late Aalenian–earliest Bajocian times, the English and Spanish palaeobiogeographical regions were connected. The ammonite assemblages revised here come from the Concavum to Ovalis zones.

The Class Asteroidea (Echinodermata): Fossils and the Base of the Crown Group

SYNOPSIS. Because of limited research, a generally accepted hypothesis has not emerged for the phylogeny of the Asteroidea. The fossil record is a potential source of needed data, although fossil asteroids are rare, and they tend to be poorly preserved. Emphasis in the taxonomy of both recent and fossil asteroids has been on characters visible from the exterior, and paleontologists have sought to fit even the most ancient (i.e., Ordovician) specimens into taxonomic ordinal schemes devised for recent asteroids. Animal form and arrangement of body wall ossicles of Paleozoic asteroids can be similar to those of younger species, thereby suggesting close affinities, yet ambulacral arrangements indicate clear separation of Paleozoic stem groups from the crown group. Traits taken from the ambulacral column that mark crown-group asteroids include presence of dorsal podial pores (which allowed transfer of the ampullae to the arm interior), an offset arrangement of ambulacrals on the adambulacrals, and increased complexity of the articulation structures between ambulacrals and adambulacrals. Transfer of ampullae to the arm interior provided protection and more space for ampullae within the arm, as well as space within the furrow and between the ambulacral and adambulacral ossicles for elaboration of the soft tissues that enhance arm motion.

Siluro-Devonian Scutelluinae (Trilobita) from the Czech Republic: morphology and classification

Complete exoskeletons of species of eight genera of Siluro-Devonian Scutelluinae show the morphology of the cephalon and thorax, particularly glabellar lobation, the wide inward extent of the doublure, and the development of fulcral processes and sockets, the latter more prominent on the external surface in stratigraphically younger species. The thorax of ten segments has axial rings with an articulating furrow and halfring as in most trilobites. The differences between the exoskeletons of Scutelluinae and Illaenidae are many, and imply anatomical differences. It is considered that Scutelluinae are related to the Ordovician Stygininae, and are to be united with them in Styginidae; a common origin for Styginidae and Illaenidae appears questionable.

Taxonomy and distribution of the buccinid gastropod Brachysphingus from uppermost Cretaceous and Lower Cenozoic marine strata of the Pacific Slope of North America

Brachysphingus is a low-spired bucciniform neogastropod known only from the fossil record of California and northern Baja California. The earliest species, Brachysphingus gibbosus Nelson, 1925, ranges in age from latest Cretaceous or possibly earliest Paleocene to the late Paleocene. During the early Paleocene, the smoothish B. gibbosus evolved into the axially ribbed B. sinuatus Gabb, 1869, which is the senior primary synonym of B. gabbi Stewart, 1927. During the late Paleocene, B. sinuatus evolved into B. mammilatus Clark and Woodford, 1927, which is the youngest species of Brachysphingus and which lasted into the early Eocene.All three species of Brachysphingus were shallow-marine dwellers subject to transport into deeper waters via turbidity currents.

The Eocene larger foraminifer Lepidocyclina ariana Cole and Ponton, from the so-called Polylepidina gardnerae horizon at Little Stave Creek, Alabama

Recent sampling for larger foraminifers in the so-called Polylepidina gardnerae horizon in the middle Eocene Lisbon Formation of the Little Stave Creek section, southwest Alabama, did not produce any examples of the lepidocyclinid foraminifer Polylepidina gardnerae Cole, but several specimens of the stratigraphically younger species, Lepidocyclina ariana Cole and Ponton, were recovered. Although the P. gardnerae horizon is named on nearly all figures of this important Gulf Coast section published since 1944, preliminary research has also failed to turn up a published basis for the identification of P. gardnerae at this locality. As L. ariana and P. gardnerae are not normally found together, it is the writer's opinion that true P. gardnerae probably has not been collected from any part of the Lisbon Formation at Little Stave Creek. If it does occur, it should be found at a lower horizon than that indicated in the literature.

A new heteromyid rodent (Mammalia) from the Barstovian (Miocene) of Saskatchewan

A new species, Harrymys canadensis, referable to the Harrymyinae (Heteromyidae), is described from the Barstovian Wood Mountain Formation of Saskatchewan. The genus Stratimus Korth et al. is included in the heteromyid subfamily Harrymyinae. Harrymys canadensis is the youngest species of the subfamily and is more derived than Stratimus or the Hemingfordian species of Harrymys. The Harrymyinae may be derived from the latest Arikareean Proheteromys matthewi Wood.