DOCSLIB.ORG

Reply to Camens: How Recently Did Modern Monotremes Diversify?

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Reply to Camens: How Recently Did Modern Monotremes Diversify? LETTER consistent with (rather than compelling evidence for) the hy- pothesis. Camens interprets the first two characteristics as fossorial adaptations and the third as absent in platypuses. Reply to Camens: How recently did However, similarly fossorial mammals such as the giant ant- modern monotremes diversify? eater and aardvark possess none of these characteristics. In contrast, hydrodynamic dorso-ventral compression and hyper- trophied humeral long-axis rotation are present in platypuses. Camens (1) responds to our analysis of morphological data (2) Finally, although the platypus hindfoot is rotated posteriorly in which platypuses (Ornithorhynchidae) and echidnas (Ta- only when swimming, it remains partly rotated (i.e., directed chyglossidae) were inferred to be each other's closest relatives, laterally) when walking—as in certain other aquatic groups to the exclusion of Early Cretaceous forms, Teinolophos and such as sea lions (Otariidae). This condition, associated with Steropodon. Our phylogeny is consistent with the late appear- aquatic habits, is a plausible precursor to the posteriorly di- ance of undisputed fossil echidnas and platypuses. Molecular rected hindfoot in echidnas. dating provided important independent corroboration, reveal- Finally, there is no evidence for the hypothesis that echidna- – ing that platypuses and echidnas diverged only 19 48 Ma, im- like monotremes have occupied myrmecophagic (ant/termite- – plying that Teinolophos and Steropodon (105 121 Ma) must lie eating) niches since the Cretaceous, to the exclusion of marsu- – outside the platypus echidna dichotomy. pials (1). Among echidnas, only Tachyglossus is myrmecophagic; Camens (1) presents different fossil evidence for an ancient both its sister taxon Zaglossus (from which it diverged <10.6 Ma: ≈ divergence, suggesting that Kryoryctes ( 105 Ma), known from Table 1 in ref. 2) and the paleontologically older fi only a fossil humerus, has af nities with echidnas. However, Megalibgwilia retained more generalized monotreme diets of such a relationship is rejected in the only published description worms and large insect larvae (5). Instead, the presence of (3), which states that “primitive features of the bone exclude the semifossorial invertebrate-feeding bandicoots and rat-kangaroos, animal concerned from the extant families Tachyglossidae and contemporaneous with the platypus–echidna divergence and Ornithorhynchidae and suggest that, if it is a monotreme, it is a pre-dating Tachyglossus (2), supports our suggestion that stem-group monotreme.” Hence, Kryoryctes does not falsify the echidnas expanded into new ecospace despite potential 19–48 Ma estimate for the platypus–echidna divergence. Sim- competition from marsupials. ilarly, “Considerable capacity for rotation digging” in Kryoryctes Matthew J. Phillipsa,1, T. H. Bennetta and Michael S. Y. Leeb,c is shared by both echidnas and platypuses and so is irrelevant for aCentre for Macroevolution and Macroecology, Research School of distinguishing terrestrial from semiaquatic origins. Indeed, as Biology, Australian National University, Canberra, ACT 0200, noted already (3), the Kryoryctes humerus could belong to the Australia; bSchool of Earth and Environmental Sciences, University contemporaneous and similarly sized Steropodon, which is a of Adelaide, SA 5005, Australia; and cEarth Sciences Section, stem monotreme (2) and probably platypus-like (4). Camens (1) South Australian Museum, Adelaide, SA 5000, Australia also suggests taphonomic biases might explain the late occur- 1. Camens AB (2009) Were early Tertiary monotremes really all aquatic? Inferring pa- rence of stem-echidnas in the fossil record. However, we con- laeobiology and phylogeny from a depauperate fossil record. Proc Natl Acad Sci USA 107:E12. sidered the absence of echidnas among abundant Oligocene/ 2. Phillips MJ, Bennett TH, Lee MSY (2009) Molecules, morphology, and ecology indicate early Miocene terrestrial mammal faunas to be consistent with a recent, amphibious ancestry for echidnas. Proc Natl Acad Sci USA 106:17089–17094. 3. Pridmore PA, Rich TH, Vickers-Rich P, Gambaryan PP (2005) A tachyglossid-like humerus (rather than compelling evidence for) recent origins and indeed from the Early Cretaceous of South-Eastern Australia. J Mammal Evol 12:359–378. offered a more compelling reason for nonpreservation: Echid- 4. Musser AM (2003) Review of the monotreme fossil record and comparison of palae- ontological and molecular data. Comp Biochem Physiol A Mol Integr Physiol 136:927–942. nas lack teeth, the most common mammal fossil remains. 5. Griffiths M, Wells RT, Barrie DJ (1991) Observations on the skulls of fossil and extant We proposed an aquatic ancestry for echidnas based on echidnas (Monotremata: Tachyglossidae). Australian Mammalogy 14:87–101. platypus-like morphology among stem-monotreme fossils pre- dating the divergence of echidnas from the platypus lineage Author contributions: T.H.B., M.J.P, and M.S.Y.L. performed research; and M.J.P. and M.S. (2, 4). Dorso-ventral compression of the body, “front-wheel Y.L. wrote the paper. drive locomotion” based on humeral long-axis rotation, and The authors declare no conflict of interest. 1 reversed hind-foot posture in echidnas again were considered To whom correspondence should be addressed. E-mail: [email protected]. www.pnas.org/cgi/doi/10.1073/pnas.0913152107 PNAS | January 26, 2010 | vol. 107 | no. 4 | E13 Downloaded by guest on September 28, 2021.
Load more

Recommended publications
  • Like Globin Genes in Monotremes and Therian Mammals
    Genomic evidence for independent origins of ␤-like globin genes in monotremes and therian mammals Juan C. Opazo*, Federico G. Hoffmann, and Jay F. Storz† School of Biological Sciences, University of Nebraska, Lincoln, NE 68588 Edited by Morris Goodman, Wayne State University School of Medicine, Detroit, MI, and approved December 13, 2007 (received for review November 5, 2007) Phylogenetic reconstructions of the ␤-globin gene family in ver- embryonic ␤-globin gene is exclusively expressed in primitive tebrates have revealed that developmentally regulated systems of erythroid cells derived from the yolk sac. However, the ‘‘␧- hemoglobin synthesis have been reinvented multiple times in globin’’ gene in birds is not orthologous to the ␧-globin gene in independent lineages. For example, the functional differentiation mammals (2, 12), because they are independently derived from of embryonic and adult ␤-like globin genes occurred independently lineage-specific duplications of a proto ␤-globin gene. in birds and mammals. In both taxa, the embryonic ␤-globin gene In placental mammals (subclass Eutheria), the ␤-globin gene is exclusively expressed in primitive erythroid cells derived from cluster includes a linked set of three early expressed (prenatal) the yolk sac. However, the ‘‘␧-globin’’ gene in birds is not ortholo- genes, ␧-␥-␩,atthe5Ј end of the cluster, and a pair of late gous to the ␧-globin gene in mammals, because they are indepen- expressed (adult) genes, ␦ and ␤,atthe3Ј end. There is extensive dently derived from lineage-specific duplications of a proto variation in the copy number of these different paralogs among ␤-globin gene. Here, we report evidence that the early and late species, and in a number of placental mammal lineages, the ␩- expressed ␤-like globin genes in monotremes and therian mam- and ␦-globin genes have been inactivated or deleted (13–15).
    [Show full text]
  • The Oldest Platypus and Its Bearing on Divergence Timing of the Platypus and Echidna Clades
    The oldest platypus and its bearing on divergence timing of the platypus and echidna clades Timothy Rowe*†, Thomas H. Rich‡§, Patricia Vickers-Rich§, Mark Springer¶, and Michael O. Woodburneʈ *Jackson School of Geosciences, University of Texas, C1100, Austin, TX 78712; ‡Museum Victoria, PO Box 666, Melbourne, Victoria 3001, Australia; §School of Geosciences, PO Box 28E, Monash University, Victoria 3800, Australia; ¶Department of Biology, University of California, Riverside, CA 92521; and ʈDepartment of Geology, Museum of Northern Arizona, Flagstaff, AZ 86001 Edited by David B. Wake, University of California, Berkeley, CA, and approved October 31, 2007 (received for review July 7, 2007) Monotremes have left a poor fossil record, and paleontology has broadly affect our understanding of early mammalian history, been virtually mute during two decades of discussion about with special implications for molecular clock estimates of basal molecular clock estimates of the timing of divergence between the divergence times. platypus and echidna clades. We describe evidence from high- Monotremata today comprises five species that form two resolution x-ray computed tomography indicating that Teinolo- distinct clades (16). The echidna clade includes one short-beaked phos, an Early Cretaceous fossil from Australia’s Flat Rocks locality species (Tachyglossus aculeatus; Australia and surrounding is- (121–112.5 Ma), lies within the crown clade Monotremata, as a lands) and three long-beaked species (Zaglossus bruijni, Z. basal platypus. Strict molecular clock estimates of the divergence bartoni, and Z. attenboroughi, all from New Guinea). The between platypus and echidnas range from 17 to 80 Ma, but platypus clade includes only Ornithorhynchus anatinus (Austra- Teinolophos suggests that the two monotreme clades were al- lia, Tasmania).
    [Show full text]
  • Two New Species of Gobiconodon (Mammalia, Eutriconodonta, Gobiconodontidae) from the Lower Cretaceous Shahai and Fuxin Formations, Northeastern China
    Historical Biology An International Journal of Paleobiology ISSN: 0891-2963 (Print) 1029-2381 (Online) Journal homepage: http://www.tandfonline.com/loi/ghbi20 Two new species of Gobiconodon (Mammalia, Eutriconodonta, Gobiconodontidae) from the Lower Cretaceous Shahai and Fuxin formations, northeastern China Nao Kusuhashi, Yuan-Qing Wang, Chuan-Kui Li & Xun Jin To cite this article: Nao Kusuhashi, Yuan-Qing Wang, Chuan-Kui Li & Xun Jin (2016) Two new species of Gobiconodon (Mammalia, Eutriconodonta, Gobiconodontidae) from the Lower Cretaceous Shahai and Fuxin formations, northeastern China, Historical Biology, 28:1-2, 14-26 To link to this article: http://dx.doi.org/10.1080/08912963.2014.977881 Published online: 01 Oct 2015. Submit your article to this journal View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ghbi20 Download by: [University of Sussex Library] Date: 01 October 2015, At: 18:24 Historical Biology, 2016 Vol. 28, Nos. 1–2, 14–26, http://dx.doi.org/10.1080/08912963.2014.977881 Two new species of Gobiconodon (Mammalia, Eutriconodonta, Gobiconodontidae) from the Lower Cretaceous Shahai and Fuxin formations, northeastern China Nao Kusuhashia*, Yuan-Qing Wangb, Chuan-Kui Lib and Xun Jinb aDepartment of Earth’s Evolution and Environment, Graduate School of Science and Engineering, Ehime University, Ehime 790-8577, Japan; bKey Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, P.R. China (Received 29 July 2014; accepted 14 October 2014) Two new gobiconodontid mammals, Gobiconodon tomidai sp.
    [Show full text]
  • Constituents of Platypus and Echidna Milk, with Particular Reference to the Fatty Acid Complement of the Triglycerides
    Aust. J. Bioi. Sci., 1984, 37, 323-9 Constituents of Platypus and Echidna Milk, with Particular Reference to the Fatty Acid Complement of the Triglycerides Mervyn Grijfiths,A,B Brian Green,A R. M. C. Leckie,A Michael Messerc and K. W. NewgrainA A Division of Wildlife and Rangelands Research, CSIRO, P.O. Box 84, Lyneham, A.C.T. 2602. B Department of Physical Biochemistry, Australian National University, G.P.O. Box 334, Canberra, A.C.T. 2601. cDepartment of Biochemistry, University of Sydney, Sydney, N.S.W. 2006. Abstract The mature milk of platypuses (Ornithorhynchus anatinus) exhibit 39· 1 gf 100 g solids, of which crude lipid accounts for 22·2% crude protein 8·2%, hexose 3·3% and sialic acid 0·43%; iron is in high concentration, 21·1 mgfl. Echidna (Tachyglossus aculeatus) milk is more concentrated, containing 48·9% solids, with lipid. protein, hexose and sialic acid accounting for 31 ·0, 12·4, 1· 6 and O· 70% respectively; it is even richer in iron, 33·3 mgfl. The fatty acid complement of milk triglyceride from platypuses living in their natural habitat is different from that of the echidna living in the wild: platypus milk triglyceride contains 17·6% palmitic, 25 . 2% oleic and c. 30% long-chain polyunsaturated acids, whereas that of echidnas exhibits 15· 9% palmitic, 61 ·2% oleic and only c. 7% polyunsaturated acids. The fatty acid complement of echidna milk triglyceride can be changed by altering the fatty acid complement of the dietary lipid. Introduction Levels of the proximate constituents, i.e. total solids, crude lipid, crude protein, carbohydrates and minerals, were determined in samples of platypus and echidna milk.
    [Show full text]
  • Short Beaked Echidna Final SAVEM
    The Short-beaked ECHIDNA Bac-yard Echidna All photos: Echidna diggings in Mallee In5ured Bea- Rachel ,estcott Species The Short-bea-ed Echidna (Tachyglossus aculeatus) is a usually solitary living monotreme found in all climatic conditions in the Australian bioregion. Echidnas can swim and climb, with home ranges up to or above 250 hectares (3 . Complete AVA SA Wildlife Admission Form. Place in SAME NA3CRA9 1IS3ARDE.. Admission and smooth plastic tub at least 50 cm in height & add handling shredded paper or straw. Restrain using (1 towels/ Echidna numbers cannot be esti- gloves to lift whole animal (2 lift gently beneath mated by numbers of diggings. ventrum without gloves (3 suspend by hind feet & Echidnas can enter torpor at any limbs'this is more stressful for the animal. time of year. Echidna —trains are Examination A conscious echidna wraps into a ball when part of courtship behaviour. touched, so complete e)amination requires chemical Breeding season is between $une restraint (see below (Schultz, pers. comm. 2012 . and September. ,eigh, assess body condition, wounds, fractures, condition of spines and bea-. Cloacal temp is 2.-320 C, 1R 2110 bpm, RR 2 10/min. Se) by everting penis. Spurs on hind limbs are not confined to males. 1ealthy animals should be released as soon as possible to the location of collection. Blood Sample from cephalic, 5ugular (near thoracic inlet), femoral or brachycephalic veins. Some clinicians Collection sample from the bea- sinus, but with great care. Anesthesia & 6asting is not required, but avoid anesthesia 6at storage in Panniculus adiposus beneath immediately after eating.
    [Show full text]
  • The White Ravens 2009 a Selection of International Children’S and Youth Literature and Youth a Selection of International Children’S
    The White Ravens 2009 A Selection of International Children’s and Youth Literature and Youth A Selection of International Children’s Internationale Jugendbibliothek The White Ravens 2009 Symbols A Selection of International ★ Special Mention – book to which we Children’s and Youth Literature wish to draw particular attention Copyright © 2009 by Internationale Jugendbibliothek ◆ book whose content is found to con- Editor: Dr. Christiane Raabe tribute to an international understanding Editorial work: Jochen Weber Translation: Frances Bottenberg among cultures and people Copy editing: Nikola von Merveldt ● book whose text is judged to be easily understandable, i.e. easy-to-read text, Selection and texts: and yet dealing with topics of interest East-Asian Languages to older readers; well-suited to foreign- Fang Weiping and Zhao Xia (Chinese) language readers and for inclusion in Fumiko Ganzenmüller (Japanese) foreign language collections of public Gumja Stiegler-Lee (Korean) and school libraries English Claudia Söffner German Ines Galling Romance Languages Doris Amberg (Romanian) Dr. Elena Kilian (French) Antonio Leoni (Italian), with the support of Gabriele Poeschke Jochen Weber (Catalan, Galician, Portuguese, Spanish), with the support of FNLIJ (IBBY Brazil) Scandinavian Languages Dr. Andreas Bode and Ines Galling (Greenlandic, Danish, Norwegian, Swedish) Ulla Christina Schwarzelühr (Finnish) Slavic and Baltic Languages Werner Küffner (Croatian, Czech, Latvian, Lithuanian, Polish, Russian, Slovak), with the support of Ulla Christina Schwarzelühr (Estonian) Other Languages Doris Amberg (Hungarian) Toin Duijx (Dutch, Frisian) Eva Kaliskami and Vassiliki Nika, IBBY Greece (Greek) Lili Sadjadi-Grübel (Arabic, Persian, Turkish) The publication of this catalogue was supported by the German Federal Ministry for Youth Affairs, the Bavarian Layout: Eva Geck State Ministry for Education, and the City of Munich.
    [Show full text]
  • Living with Echidnas
    Living with Echidnas Keywords: monotremes, mammals. puggle, invertebrates Location: Southwest Author: Robert Huston What is an echidna primitive and special mammal whose presence on the Australian continent has been traced back over 150 Echidnas are one of Australia's most unique and million years. widely spread of all native mammals. Their name is In the monotreme group there are only three known derived from the Greek goddess Ekhidna who was half species; the short nosed echidna (Tachyglossus snake (reptile) and half woman (mammal). It is this aculeatus), the long nosed echidna (Zaglossus mixture of reptilian and mammalian characters which bruijnii) and the platypus (Ornithorhynchus classifies this species into a special group of mammals anatinus). The short nosed echidna species is common called monotremes. Mammals as a whole are to Australia and the long nosed echidna is native only to characterized by a number of general qualities such as New Guinea. Within Australia there are four subspecies having fur, breathe using lungs, warm blooded and the ranging from the mainland states across to Tasmania and young suckle milk from their mother. Monotremes have Kangaroo Island off South Australia. In West Australia all these mammalian characteristics plus one other unique we have the variety Tachyglossus aculeatu, quality which sets them apart. They lay soft shelled eggs acanthion, which is also common in the arid zones of all from which their young hatch. Echidnas represent a very the mainland states. Characteristics and Habits SPINES Probably the most recognizable characteristic of echidnas are the many sharp spines covering their back and sides. Each spine is connected to a bundle of muscles which allows the animal to very quickly erect them as a formidable protective shield.
    [Show full text]
  • Three Types of Mammals by Cindy Grigg
    Three Types of Mammals By Cindy Grigg 1 Earth has a large variety of animals living on it. Scientists classify animals into groups based on common characteristics. Mammals are a group of animals (vertebrates) that have backbones and hair or fur. They are warm-blooded (endothermic), and they have four-chambered hearts. They also feed their young with milk from the mother's body. The young of most mammals are born alive. 2 Mammals have about six thousand different species, or kinds, of animals in their group or class. Mammals can be divided into three more groups based on how their babies develop. These three groups are monotremes, marsupials, and the largest group, placental mammals. 3 Monotremes are mammals that lay eggs. The only monotremes that are alive today are the spiny anteater, or echidna, and the platypus. They live in Australia, Tasmania, and New Guinea. These mammals are really different from other mammals. Their body temperature is lower than most warm-blooded animals, a feature that has more in common with reptiles. Their name comes from the fact that they have only one body opening for both wastes and eggs to pass through. Echidnas have sharp spines scattered throughout their hair. They look like a spiky ball. The female anteater lays usually one leathery-shelled egg directly into the pouch on her belly. The egg hatches after only ten or eleven days. The newborn baby is tiny, about the size of a dime. After the baby hatches, it stays in the pouch for several weeks and continues to develop.
    [Show full text]
  • Molecules, Morphology, and Ecology Indicate a Recent, Amphibious Ancestry for Echidnas
    Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas Matthew J. Phillipsa,1, Thomas H. Bennetta, and Michael S. Y. Leeb,c aCentre for Macroevolution and Macroecology, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia; bSchool of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia; and cEarth Sciences Section, South Australian Museum, Adelaide, SA 5000, Australia Edited by David B. Wake, University of California, Berkeley, CA, and approved August 14, 2009 (received for review April 28, 2009) The semiaquatic platypus and terrestrial echidnas (spiny anteaters) Fossil echidnas do not appear until the mid-Miocene (Ϸ13 are the only living egg-laying mammals (monotremes). The fossil Ma) (13), despite excellent late Oligocene–Early Miocene mam- record has provided few clues as to their origins and the evolution mal fossil records in both northern and southern Australia. This of their ecological specializations; however, recent reassignment absence has tentatively been attributed in part to echidnas of the Early Cretaceous Teinolophos and Steropodon to the platy- lacking teeth (14), which are the most common fossil remains pus lineage implies that platypuses and echidnas diverged >112.5 from mammals. Alternatively, if the molecular dating studies million years ago, reinforcing the notion of monotremes as living that estimate the divergence of echidnas from platypuses at fossils. This placement is based primarily on characters related to 17–35 Ma (15–22) are correct, then characters that clearly ally a single feature, the enlarged mandibular canal, which supplies fossil taxa with echidnas would not be expected to have evolved blood vessels and dense electrosensory receptors to the platypus until even more recently.
    [Show full text]
  • 17. Morphology and Physiology of the Metatheria
    FAUNA of AUSTRALIA 17. MORPHOLOGY AND PHYSIOLOGY OF THE METATHERIA T.J. DAWSON, E. FINCH, L. FREEDMAN, I.D. HUME, MARILYN B. RENFREE & P.D. TEMPLE-SMITH 1 17. MORPHOLOGY AND PHYSIOLOGY OF THE METATHERIA 2 17. MORPHOLOGY AND PHYSIOLOGY OF THE METATHERIA EXTERNAL CHARACTERISTICS The Metatheria, comprising a single order, Marsupialia, is a large and diverse group of animals and exhibits a considerable range of variation in external features. The variation found is intimately related to the animals' habits and, in most instances, parallels that are found in the Eutheria. Useful general references to external characteristics include Pocock (1921), Jones (1923a, 1924), Grassé (1955), Frith & Calaby (1969), Ride (1970) and Strahan (1983). Body form In size, the marsupials range upwards from the Long-tailed Planigale, Planigale ingrami, a small, mouse-like animal weighing only around 4.2 g, with a head- body length of 59 mm and a tail 55 mm long. At the other extreme, there are large kangaroos, such as the Red Kangaroo, Macropus rufus, in which the males may weigh as much as 85 kg and attain a head-body length of 1400 mm and a tail of 1000 mm. Body shape also varies greatly. The primarily carnivorous marsupials, the dasyurids (for example, antechinuses, dunnarts, quolls, planigales and others), are small to medium sized quadrupeds with subequal limbs. The tail is relatively slender and generally about half the length of the body. The omnivorous peramelids show increased development of the hind limbs in keeping with their rapid bounding locomotion. Saltatory or hopping forms (for example kangaroos and wallabies), carry the hind limb specialisation to an extreme, with a concomitant reduction of the forelimbs (Fig.
    [Show full text]
  • The Miocene Mammal Necrolestes Demonstrates the Survival of a Mesozoic Nontherian Lineage Into the Late Cenozoic of South America
    The Miocene mammal Necrolestes demonstrates the survival of a Mesozoic nontherian lineage into the late Cenozoic of South America Guillermo W. Rougiera,b,1, John R. Wibleb, Robin M. D. Beckc, and Sebastian Apesteguíad,e aDepartment of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, KY 40202; bSection of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA 15206; cSchool of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia; dCEBBAD–Fundación de Historia Natural ‘Félix de Azara’, Universidad Maimónides, 1405 Buenos Aires, Argentina; and eConsejo Nacional de Investigaciones Científicas y Técnicas de Argentina, C1033AAJ Buenos Aires, Argentina Edited by Richard L. Cifelli, University of Oklahoma, Norman, OK, and accepted by the Editorial Board October 18, 2012 (received for review July 27, 2012) The early Miocene mammal Necrolestes patagonensis from Pata- not referable to either Metatheria or Eutheria, but did not discuss gonia, Argentina, was described in 1891 as the only known extinct the evidence for this interpretation, nor did they identify the placental “insectivore” from South America (SA). Since then, and specific therian lineages they considered to be potential relatives despite the discovery of additional well-preserved material, the of Necrolestes. Starting in 2007, we oversaw additional prepara- systematic status of Necrolestes has remained in flux, with earlier tion of Necrolestes specimens that comprise the best-preserved studies leaning toward placental affinities and more recent ones material currently available, including skulls, jaws, and some iso- endorsing either therian or specifically metatherian relationships. We lated postcranial bones; as a result, many phylogenetically signif- have further prepared the best-preserved specimens of Necrolestes icant features have been revealed for the first time.
    [Show full text]
  • New Data on the Paleocene Monotreme Monotrematum Sudamericanum, and the Convergent Evolution of Triangulate Molars
    New data on the Paleocene monotreme Monotrematum sudamericanum, and the convergent evolution of triangulate molars ROSENDO PASCUAL, FRANCISCO J. GOIN, LUCÍA BALARINO, and DANIEL E. UDRIZAR SAUTHIER Pascual, R., Goin, F.J., Balarino, L., and Udrizar Sauthier, D.E. 2002. New data on the Paleocene monotreme Monotrematum sudamericanum, and the convergent evolution of triangulate molars. Acta Palaeontologica Polonica 47 (3): 487–492. We describe an additional fragmentary upper molar and the first lower molar known of Monotrematum sudamericanum, the oldest Cenozoic (Paleocene) monotreme. Comparisons suggest that the monotreme evolution passed through a stage in which their molars were “pseudo−triangulate”, without a true trigonid, and that the monotreme pseudo−triangulate pat− tern did not arise through rotation of the primary molar cusps. Monotreme lower molars lack a talonid, and consequently there is no basin with facets produced by the wearing action of a “protocone”; a cristid obliqua connecting the “talonid“ to the “trigonid” is also absent. We hypothesize that acquisition of the molar pattern seen in Steropodon galmani (Early Cre− taceous, Albian) followed a process similar to that already postulated for docodonts (Docodon in Laurasia, Reigitherium in the South American sector of Gondwana) and, probably, in the gondwanathere Ferugliotherium. Key words: Monotremata, Monotrematum, pseudo−triangulate molars, molar structure, Gondwana, Patagonia, Paleocene. Rosendo Pascual [[email protected]], Francisco Goin [[email protected]], Lucía Balarino, and Daniel Udrizar Sauthier, Departamento Paleontología Vertebrados, Museo de la Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina. Introduction Systematic paleontology The relationships of Monotremata have been widely debated Monotremata Bonaparte, 1837 in recent years, with little apparent consensus (e.g., Kühne Ornithorhynchidae Gray, 1825 1977; Kielan−Jaworowska et al.
    [Show full text]