Shecenia Temporal range: Late Paleocene-Early Eocene ~57–54 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Astrapotheria
Genus:	†Shecenia Simpson 1935
Type species
Shecenia ctirneru Simpson, 1935
Species
S. ctirneru Simpson 1935

Shecenia is an extinct genus of mammal, probably belonging to the order Astrapotheria. It lived between the Late Paleocene and the Early Eocene, and its fossilized remains were found in South America.

This animal is known from very fragmentary remains, including a partial mandible. Its relatives, the astrapotheres, vaguely resembled tapirs.

The mandibular symphysis was quite long and flat on the interior surface. it had two pairs of small incisors, framed posteriorly and a bit laterally by a pair of very strong, long-rooted, very curved and forward-protruding teeth. Behind them was a large diastema, followed by another pair of very strong teeth, slightly curved forward but with a short root. These two teeth were approximately located near the middle of the symphysis. Like Trigonostylops, the symphysis of Shecenia had a flat lower edge.

Shecenia was first described in 1935 by George Gaylord Simpson, based on fossils found in probably Lower Eocene terrains from Argentina. The type species is Shecenia ctirneru, but other remains from the Late Paleocene have also been attributed to the genus.

Shecenia is considered an archaic astrapothere, a mysterious group of South American mammals, vaguely reminding of tapirs. Shecenia is considered to be a member of Trigonostylopidae, a clade comprising some of the oldest and more archaic members of Astrapotheria.

• G. G. Simpson. 1935. Descriptions of the oldest known South American mammals, from the Rio Chico Formation. American Museum Novitates 793:1-25
• G. G. Simpson. 1967. The beginning of the age of mammals in South America. Part II. Bulletin of the American Museum of Natural History 137:1-260
• M. O. Woodburne, F. J. Goin, M. S. Raigemborn, M. Heizler, J. N. Gelfo and E. V. Oliveira. 2014. Revised timing of the South American early Paleogene land mammal ages. Journal of South American Earth Sciences 54:109-119

v t e Genera of South American native ungulates
Kingdom: Animalia Phylum: Chordata Class: Mammalia Superorder: Laurasiatheria
Xenungulata, Pyrotheria, Astrapotheria, and other minor groups †Kollpaniidae? Andinodus Molinodus Pascualodus? Pucanodus Simoclaenus Tiuclaenus †Didolodontidae Didolodus Enneoconus Ernestokokenia Escribania? Lamegoia Paulogervaisia Raulvaccia Ricardocifellia Saltaodus Umayodus Xesmodon †Protolipternidae Asmithwoodwardia Miguelsoria Protolipterna †Xenungulata †Carodniidae Carodnia Etayoa Notoetayoa Rodcania †Pyrotheria †Colombitheriidae Colombitherium Proticia †Pyrotheriidae Baguatherium Berracotherium Carolozittelia Griphodon Propyrotherium Pyrotherium †Astrapotheria Eoastrapostylops †Trigonostylopidae Shecenia Tetragonostylops Trigonostylops †Astrapotheriidae Antarctodon Astrapodon Comahuetherium Liarthrus Maddenia Parastrapotherium †Albertogaudryinae Albertogaudrya Astraponotus †Astrapotheriinae Astrapothericulus Astrapotherium Scaglia †Uruguaytheriinae Granastrapotherium Hilarcotherium Uruguaytherium Xenastrapotherium
Litopterna †Eulitopterna †Adianthidae Adianthus Proadiantus Proectocion? Proheptaconus Thadanius Tricoelodus †Macraucheniidae Polymorphis †Cramaucheniinae Caliphrium Coniopternium Cramauchenia Llullataruca Phoenixauchenia Pternoconius Theosodon †Macraucheniinae Cullinia Huayqueriana Macrauchenia Macraucheniopsis Micrauchenia Oxyodontherium Paranauchenia Promacrauchenia Scalabrinitherium Windhausenia Xenorhinotherium †Proterotherioidea †Anisolambdidae †Anisolambdinae Anisolambda Eolicaphrium Guilielmofloweria Lambdaconops Paranisolambda Polyacrodon Protheosodon Wainka †Sparnotheriodontinae Heteroglyphis Notiolofos Phoradiadius Sparnotheriodon Victorlemoinea †Proterotheriidae Mesolicaphrium Neodolodus Olisanophus Promylophis Prothoatherium Pseudobrachytherium Salladolodus †Megadolodinae Bounodus Megadolodus †Proterotheriinae Anisolophus Brachytherium Diadiaphorus Diplasiotherium Eoauchenia Epecuenia Epitherium Lambdaconus Neobrachytherium Neolicaphrium Paramacrauchenia Picturotherium Prolicaphrium Proterotherium Tetramerorhinus Thoatheriopsis Thoatherium Uruguayodon Villarroelia †Notopterna †Amilnedwardsiidae Amilnedwardsia Ernestohaeckelia Rutimeyeria †Indaleciidae Adiantoides Indalecia †Notonychopidae Notonychops Requisia Incertae sedis Kyraodus Proacrodon
Notoungulata incertae sedis Acoelodus Archaeogaia Carolodarwinia Perutherium †Notioprogonia Satshatemnus Seudenius †Henricosborniidae Henricosbornia Nanolophodon Othnielmarshia Peripantostylops Simpsonotus †Notostylopidae Boreastylops Chilestylops Edvardotrouessartia Homalostylops Notostylops Otrhonia Parastylops †Toxodontia †Homalodotheriidae Asmodeus Chasicotherium Homalodotherium Trigonolophodon †Isotemnidae Anisotemnus Coelostylodon Distylophorus Hedralophus Isotemnus Lophocoelus Pampatemnus Periphragnis Pleurocoelodon Pleurostylodon Rhyphodon Thomashuxleya †Eutoxodontia †Leontiniidae Anayatherium Ancylocoelus Colpodon Coquenia Elmerriggsia Gualta Henricofilholia Huilatherium Leontinia Martinmiguelia Purperia? Scarrittia Taubatherium Termastherium †Notohippidae Acoelohyrax Argyrohippus Deuterotherium? Edvardocopeia Eomorphippus Eurygenium Mendozahippus Moqueguahippus Morphippus Nesohippus Notohippus Pampahippus Pascualihippus Patagonhippus Perhippidion Plexotemnus Puelia Purperia? Rhynchippus Rosendo Stilhippus Teushentherium Trimerostephanos †Toxodontidae †Nesodontinae Adinotherium Nesodon Proadinotherium †Toxodontinae Abothrodon Andinotoxodon Calchaquitherium Ceratoxodon Charruatoxodon Dinotoxodon Eutomodus Falcontoxodon Gyrinodon Haplodontherium Hemixotodon Hoffstetterius Hyperoxotodon Mesenodon Mesotoxodon Minitoxodon Mixotoxodon Neoadinotherium Neotoxodon Nesodonopsis Nonotherium Ocnerotherium Palyeidodon Paratrigodon Pericotoxodon Piauhytherium Pisanodon Plesiotoxodon Posnanskytherium Prototrigodon Stenotephanos Stereotoxodon Toxodon Toxodontherium Trigodon Trigodonops Xotodon †Typotheria Campanorco Griphotherion †Archaeopithecidae Archaeopithecus Teratopithecus †Oldfieldthomasiidae Allalmeia Brachystephanus Camargomendesia Colbertia Dolichostylodon Itaboraitherium Kibenikhoria Maxschlosseria Oldfieldthomasia Paginula Suniodon Tsamnichoria Ultrapithecus Xenostephanus †Interatheriidae Antofagastia Ignigena Johnbell Munizia Punapithecus †Interatheriinae Archaeophylus Argyrohyrax Boleatherium Brucemacfaddenia Caenophilus Choichephilum Cochilius Eopachyrucos Federicoanaya Interatherium Juchuysillu Miocochilius Neoicochilus Patriarchus Proargyrohyrax Progaleopithecus Protypotherium Santiagorothia †Notopithecinae Antepithecus Guilielmoscottia Notopithecus Transpithecus †Mesotheriidae Fiandraia? Trachytherus †Mesotheriinae Altitypotherium Caraguatypotherium Eotypotherium Eutypotherium Hypsitherium Mesotherium Microtypotherium Plesiotypotherium Pseudotypotherium Rusconitherium Typotheriopsis †Archaeohyracidae Archaeohyrax Archaeotypotherium Bryanpattersonia Eohyrax Pascualhyrax Protarchaeohyrax Pseudhyrax Punahyrax †Hegetotheriidae †Hegetotheriinae Ethegotherium Hegetotheriopsis Hegetotherium Hemihegetotherium Prohegetotherium Pseudohegetotherium Sallatherium †Pachyrukhinae Medistylus Propachyrucos Prosotherium Tremacyllus †Pachyrukhini Pachyrukhos Paedotherium Tremacyllus