Gondwanatheria

Gondwanatheres Temporal range:
Skull ofAdalatherium
Mandible ofSudamerica
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Subclass:	†Allotheria(?)
Clade:	†Gondwanatheria Mones,1987
Subgroups
?†Allostaffia Family†Sudamericidae †Bharattherium †Galulatherium? †Gondwanatherium †Lavanify †Patagonia †Sudamerica †Vintana Family †Ferugliotheriidae †Ferugliotherium †Trapalcotherium (?) †Argentodites (?) †Magallanodon Family †Adalatheriidae †Adalatherium Family †GroeberiidaePatterson, 1952 †Groeberia ?†Klohnia ?†Epiklohnia ?†Praedens Family unknown †Greniodon

Gondwanatheriais an extinct group ofmammaliaformsthat lived in parts ofGondwana,including Madagascar, India, South America, Africa, and Antarctica during theUpper Cretaceousthrough thePaleogene(and possibly much earlier, ifAllostaffiais a member of this group). Until recently, they were known only from fragmentary remains.They are generally considered to be closely related to themultituberculatesand likely theeuharamiyidians,well known from the Northern Hemisphere, with which they form the cladeAllotheria.

Classification

Life reconstruction ofVintana sertichi.Postcranial reconstruction is hypothetical.

For several decades the affinities of the group were not clear, being first interpreted as earlyxenarthrans,or "toothless" mammals similar to the modernanteater.A variety of studies have placed them asallotheresrelated tomultituberculates,possibly even true multituberculates, closer tocimolodontsthan "plagiaulacidans"are.However, a more recent study recovered them as nested amongharamiyidans,rendering them as non-mammalian cynodonts.A more recently described specimen has since recovered them as allotheres closely related tomultituberculates,but this was soon after followed by a study recovering them as part ofEuharamiyida,which itself was placed inside crown-group Mammalia.

There are three knownfamilieswithin Gondwanatheria. The family Sudamericidae was named by Scillato-Yané and Pascual in 1984, and includes the vast majority of named taxa. The family Ferugliotheriidae was named byJosé Bonapartein 1986, and includes one genus,Ferugliotherium,and possibly a few other forms likeTrapalcotheriumfrom the Late Cretaceous of South America. Ferugliotheriidae are considered the most basal gondawanatherians, and are sometimes recovered outside the group.

Gondwanatheria cladogram per Chimento et al. 2015.

Furtherfossilshave come fromIndia,Madagascarand Antarctica. A possibleFerugliotherium-like species occurs inMaastrichtiandeposits ofMexico,extending the clade toNorth America.

The youngest gondwanatherians are known from theEoceneof South America and Antarctica.The Eocene genusGroeberiaand Miocene genusPatagonia,two mammals from South America with unusual tooth morphologies usually consideredmetatherians,were considered by one paper to be gondwanatheres.However, their conclusions have generally not been accepted.

Biology

Gondwanatheres known from cranial remains almost universally have deep, robust snouts, as befitting their specialised herbivorous lifestyle.Vintanapossesses bizarrejugalflanges similar to those ofxenarthranslikeground sloths,though they had a palinal (front-to-back) chewing method as in most allotheres and unlike almost anytherian.Most gondwanatheres are specialisedgrazers,even being among the first mammals to have specialised forgrass-eatinglong before any therians did, with the exceptions ofGroeberidaeandFerugliotheriidae,which lack hypsodont teeth and therefore had more generalistic herbivorous habits.

An articulated specimen found in theMaevarano Formationoffers insight to the postcranial skeleton of these animals. Among the bizarre and unique features are a mediolaterally compressed and antero-posteriorly bowed tibia, a doubletrochlea(grooved structure) on thetalus bone,a fully developedhumeral trochlea,and an unusually high number of trunk vertebrae. The new taxon has at least 19 rib-bearing (thoracic) and 11 non-rib-bearing (lumbar) vertebrae. Aside from these derived features, the Malagasy mammal has a mosaic pectoral girdle morphology: the procoracoid is lost, thecoracoidis extremely well developed (into an enlarged process that contributes to half of theglenoid fossa), the interclavicle is small, and thesternoclavicular jointappears mobile. A ventrally-facing glenoid and the well-developed humeral trochlea suggest a relatively parasagittal posture for the forelimbs. Remarkable features of the hind limb and pelvic girdle include a largeobturator foramensimilar in size to that oftherians,a large parafibula, and the presence of anepipubicbone.

The fully described animal, now namedAdalatherium hui,is a comparatively large sized mammal, compared in size to a large cat. It has more erect limbs than other allotheres.

Taxonomy

Order †GondwanatheriaMcKenna 1971[GondwanatheroideaKrause & Bonaparte 1993]

• ?†Allostaffia
• †Adalatherium
• ?†Galulatherium
• Family †FerugliotheriidaeBonaparte 1986
  • †Ferugliotherium windhauseniBonaparte 1986a[VucetichiaBonaparte 1990;Vucetichia gracilisBonaparte 1990]
  • †Trapalcotherium matuastensisRougier et al. 2008
  • ?†Magallanodon baikashkenkeGoin et al. 2020
• Family †SudamericidaeScillato-Yané & Pascual 1984[GondwanatheridaeBonaparte 1986]
  • †Greniodon sylvanicumGoin et al. 2012
  • †Vintana sertichiKrause et al. 2014
  • †Dakshina jederiWilson, Das Sarama & Anantharaman 2007
  • †Gondwanatherium patagonicumBonaparte 1986
  • †Sudamerica ameghinoiScillato-Yané & Pascual 1984
  • †Lavanify miolakaKrause et al. 1997
  • †Bharattherium bonaparteiPrasad et al. 2007
  • †Patagonia peregrinaPascual & Carlini 1987
  • †GalulatheriumO'Connor et al. 2019

External links

• Mesozoic Mammals - Gondwanatheria