Project 1070: Christian De Muizon,Guillaume Billet,Christine Argot,Sandrine Ladevèze,Florent Goussard. 2015. Alcidedorbignya inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny and palaeobiology. Geodiversitas. 37 (4):397-634.
Specimen: MHNC/8372
View: Lateral views

Abstract

Alcidedorbignya inopinata Muizon & Marshall, 1987 is a basal pantodont (Placentalia, Mammalia) of small body size, from the early Palaeocene of the Santa Lucia Formation at Tiupampa, Bolivia. Tiupampa is the type locality for the Tiupampan, a South American Land Mammal age (SALMA), which is assigned an age equivalent to the basal Torrejonian 1 of North America (c. 65 Ma). Alcidedorbignya is known by exceptionally preserved specimens, which are described here. The two major specimens are an almost complete skeleton (MHNC 8372) and a partial skull (MHNC 8399), the former representing one of the best-preserved fossil placentals from the early Palaeocene and probably the oldest placental skeleton that is so completely known. These specimens are also the first eutherian skulls and skeleton ever discovered at Tiupampa, a locality which has yielded numerous metatherian skulls and partial skeletons. The remarkable preservation of the two skulls allows a detailed description of the cranial anatomy with well-identified sutures and foramina, including those of the auditory region. Through CT scanning of the skulls, the arterial and venous circulation pattern in the basicranium as well as the bony labyrinth of the inner ear were tentatively reconstructed. A thorough description of the postcranial skeleton of MHNC 8372 is also provided. Among pantodonts, Alcidedorbignya presents the closest morphological similarities with Pantolambda, the oldest and earliest diverging North American pantodont (known by skulls and skeletons), from the late early Palaeocene (Torrejonian 2 and 3) of New Mexico. Alcidedorbignya is one-third the size, much more gracile, and clearly exhibits more plesiomorphic features than Pantolambda. It is also at least 3 Ma older. Interesting similarities are also observed between the skull of Alcidedorbignya and several “condylarths”, such as Maiorana, Baioconodon, Arctocyon, and Arctocyonides. The basicranium of Alcidedorbignya is also similar to that of some extant afrotheres (e.g., Tenrec) or Lipotyphla (e.g., Solenodon), but most of these similarities may represent placental symplesiomorphies. In fact, the cranial anatomy of Alcidedorbignya, beyond the simple thorough description of a basal pantodont, sheds light on the cranial anatomy of placentals from the earliest Paleocene, previously unknown in this detail. The postcranial skeleton of MHNC 8372 together with some isolated specimens referred to A. inopinata, is compared to adequate morphofunctional models (e.g., Solenodon, Dendrohyrax, Sciurus), which indicates that it was a moderately agile, plantigrade, generalized terrestrial mammal with good climbing ability (scansorial) and occasionally capable of standing in a bipedal position. The scutiform ungual phalanges were probably bearing nail-like hooves (or primate-like nails) and because of the absence of claws, fossorial habits are unlikely.

A parsimony analysis of a data matrix including 72 taxa and 426 characters (cranial and postcranial) has been undertaken with TNT and Paup 4b10. The matrix includes several stem eutherians and representatives of the four major clades of Placentalia: Laurasiatheria, Euarchontoglires, Xenarthra, and Afrotheria. Furthermore, because one of the major aims of this analysis is to test possible close phylogenetic relationships of Alcidedorbignya inopinata with the five orders of South American “ungulates”, 12 taxa belonging to the Notoungulata, Astrapotheria, Litopterna, Pyrotheria and Xenungulata, were included in the matrix. Two analyses were performed: one unconstrained and one with a backbone constraint based on the latest molecular phylogenies. One of the main results of these analyses is the high level of homoplasy detected by the low retention index (RI close to 0.5; CI inferior to 0.2), which indicates that half of the similarities present in the matrix are interpreted as homoplasies. Nevertheless, some interesting observations emerge. In both analyses, all members of Pantodonta are closely related and included in the Placentalia, and the Eocene “cimolestid” taxon Didelphodus, which has been regarded as closely related to pantodonts, is their sister-group. In the constrained analysis, the Pantodonta are monophyletic and included in the Laurasiatheria; Didelphodus and the pantodonts are clustered with the Tillodontia, either as their sister group or included in a clade also comprising some “condylarths”. In the unconstrained analysis the xenungulate Carodnia is included within the Pantodonta as the sister group of Coryphodon, this clade being part of a large basal polytomy of placental lineages. Both analyses agree with a northern origin of the South American pantodont Alcidedorbignya as it is nested within northern taxa. Furthermore, no close relationship of Alcidedorbignya with South American endemic ungulates is supported, except for pantodont-xenungulate affinities in the unconstrained analysis. In the constrained analysis the five groups of South American endemic “ungulates” are gathered in a single clade included in the laurasiatheres but not directly related to pantodonts. Finally, the rather apical position of Alcidedorbignya in both analyses may be considered as an argument for a pre-K-Pg placental diversification, as this taxon is dated at c. 65 Ma, nearly coincident with the end of the Cretaceous.



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Article DOI: http://dx.doi.org/10.5252/g2015n4a1

Project DOI: 10.7934/P1070, http://dx.doi.org/10.7934/P1070
This project containsMatrices
  • 1 Media
  • 1 Matrix
  • 72 Taxa
  • 1 Specimen
  • 426 Characters
Total size of project's media files: 6 MB

Download Project SDD File
Total scored cells: 23911
Total media associated with cells: 0
Total labels associated with cell media: 0
Characters
Total characters: 426
Total characters with associated media: 0
Total characters with media with labels: 0
Total character states: 1043
Total character states with associated media: 0
Total character states with media with labels:0
Total unordered/ordered characters:360/66
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MorphoBank Project 1070


    Members

    member name taxa specimens media chars character
    media
    labels
    cell scorings
    (scored, NPA, "-")
    cell
    medialabels
    rules
    Guillaume Billet
    Project Administrator
    Last logged in 11/06/17
    59004260016066
    (14918, 0, 1148)
    000
    Maureen Admin
    Full membership
    Last logged in 01/13/16
    0000000
    (0, 0, 0)
    000
    MorphoBank Curator
    Full membership
    Last logged in 01/12/16
    0100000
    (0, 0, 0)
    000
    Christian Muizon
    Full membership
    Last logged in 11/06/17
    13010007845
    (7247, 0, 598)
    003


    Taxonomic Overview for Matrix 'M2350' (72 Taxa)

    taxon unscored
    cells
    scored
    cells
    no cell
    support
    NPA
    cells
    "-" cellscell images labels on
    cell images
    member
    access
    [1] † Vincelestes
    Last Modified in 11/06/17
    12386385029004
    [2] † Deltatheridium
    Last Modified in 11/06/17
    151266265010004
    [3] † Mayulestes
    Last Modified in 11/06/17
    41368368017004
    [4] † Pucadelphys
    Last Modified in 11/06/17
    9406403014004
    [5] † Eomaia
    Last Modified in 11/06/17
    23519018803004
    [6] † Prokennalestes
    Last Modified in 11/06/17
    23119719203004
    [7] † Zhelestes
    Last Modified in 11/06/17
    26017016402004
    [8] † Cimolestes
    Last Modified in 11/06/17
    26117116203004
    [9] † Maelestes
    Last Modified in 11/06/17
    11132131302004
    [10] † Kennalestes
    Last Modified in 11/06/17
    104315311011004
    [11] † Asioryctes
    Last Modified in 11/06/17
    63355349013004
    [12] † Kulbeckia
    Last Modified in 11/06/17
    22020419709004
    [13] † Zalambdalestes
    Last Modified in 11/06/17
    38391377011004
    [14] † Leptictis
    Last Modified in 11/06/17
    1240740608004
    [15] † Didelphodus
    Last Modified in 11/06/17
    23418918804004
    [16] † Alcidedorbignya
    Last Modified in 11/06/17
    042142006004
    [17] † Pantolambda
    Last Modified in 11/06/17
    2639539406004
    [18] † Bemalambda
    Last Modified in 11/06/17
    10931531304004
    [19] † Harpyodus
    Last Modified in 11/06/17
    340868600004
    [20] † Coryphodon
    Last Modified in 11/06/17
    10831731404004
    [21] † Azygonyx-Esthonyx
    Last Modified in 11/06/17
    13628528406004
    [22] † Trogosus
    Last Modified in 11/06/17
    95322319012004
    [23] † Protungulatum
    Last Modified in 11/06/17
    21121921104004
    [24] † Vulpavus
    Last Modified in 11/06/17
    7635934307004
    [25] † Miacis
    Last Modified in 11/06/17
    9533332506004
    [26] † Cynodictis
    Last Modified in 11/06/17
    10831330908004
    [27] † Diacodexis
    Last Modified in 11/06/17
    8333933508004
    [28] † Dichobune
    Last Modified in 11/06/17
    12929229106004
    [29] † Acotherulum
    Last Modified in 11/06/17
    13029228907004
    [30] † Hyopsodus
    Last Modified in 11/06/17
    18408395013004
    [31] † Meniscotherium
    Last Modified in 11/06/17
    15404398013004
    [32] † Phenacodus
    Last Modified in 11/06/17
    35386377014004
    [33] † Pleuraspidotherium
    Last Modified in 11/06/17
    3738338009004
    [34] † Maiorana
    Last Modified in 11/06/17
    15326826805004
    [35] † Baioconodon
    Last Modified in 11/06/17
    16026326204004
    [36] † Arctocyonides
    Last Modified in 11/06/17
    9932131908004
    [37] † Arctocyon
    Last Modified in 11/06/17
    40374372014004
    [38] Ptilocercus
    Last Modified in 12/05/13
    4412408014004
    [39] † Plesiadapis
    Last Modified in 11/06/17
    33390373020004
    [40] † Northarctus
    Last Modified in 11/06/17
    39376369018004
    [41] † Adapis-Magnadapis
    Last Modified in 11/06/17
    54364354018004
    [42] † Tribosphenomys
    Last Modified in 11/06/17
    243153153030004
    [43] † Paramys
    Last Modified in 11/06/17
    32354349045004
    [44] † Rhombomylus
    Last Modified in 11/06/17
    22368360044004
    [45] † Gomphos
    Last Modified in 11/06/17
    101288286039004
    [46] † Mimotona
    Last Modified in 11/06/17
    266130126034004
    [47] Blarina
    Last Modified in 12/05/13
    21382373032004
    [48] Erinaceus
    Last Modified in 12/05/13
    2414402022004
    [49] Solenodon
    Last Modified in 12/05/13
    8400391027004
    [50] † Eoryctes
    Last Modified in 11/06/17
    204215210012004
    [51] Potamogale
    Last Modified in 12/05/13
    7392391028004
    [52] Tenrec
    Last Modified in 12/05/13
    8396389029004
    [53] Orycteropus
    Last Modified in 12/05/13
    102932870129004
    [54] Rhynchocyon
    Last Modified in 12/05/13
    18380378030004
    [55] Procavia
    Last Modified in 12/05/13
    1404395030004
    [56] † Moeritherium
    Last Modified in 11/06/17
    111279277038004
    [57] Chaetophractus
    Last Modified in 12/05/13
    22872870137004
    [58] Dasypus
    Last Modified in 12/05/13
    12772760149004
    [59] Bradypus
    Last Modified in 12/05/13
    42772730149004
    [60] Tamandua
    Last Modified in 12/05/13
    162472450165004
    [61] † Colbertia
    Last Modified in 11/06/17
    144275270012004
    [62] † Plesiotypotherium
    Last Modified in 11/06/17
    131271263032004
    [63] † Protypotherium
    Last Modified in 11/06/17
    106315306014004
    [64] † Adinotherium
    Last Modified in 11/06/17
    95331320011004
    [65] † Notostylops
    Last Modified in 11/06/17
    129301284013004
    [66] † Pyrotherium
    Last Modified in 11/06/17
    185218211030004
    [67] † Trigonostylops
    Last Modified in 11/06/17
    186231226014004
    [68] † Astrapotherium
    Last Modified in 11/06/17
    120282272034004
    [69] † Miguelsoria
    Last Modified in 11/06/17
    22419719606004
    [70] † Proterotherium
    Last Modified in 11/06/17
    55362353018004
    [71] † Macrauchenia
    Last Modified in 11/06/17
    119301296011004
    [72] † Carodnia
    Last Modified in 11/06/17
    24717217009004


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    Project overview354
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    Matrix views239Matrix landing page (198 views); Pantod matrix (41 views);
    Taxon list826
    Specimen list118
    Views for media list89
    Bibliography88




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    type number of downloads Individual items downloaded (where applicable)
    Total downloads from project34
    Matrix downloads7Pantod matrix (7 downloads);
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