Die kopbeen van *A. ajax*, voorwerp CMC VP 7180.

***Apatosaurus*** ("misleidende akkedis") is ’n genus van souropode-dinosourusse wat in die Laat Jura-periode in Noord-Amerika voorgekom het. Dit is aanvanklik in 1877 deur Othniel Charles Marsh beskryf en hy het die eerste bekende spesie *Apatosaurus ajax* genoem en die tweede spesie, wat in 1916 ontdek is, *Apatosaurus louisae*. Hulle is tussen 152 miljoen en 151 miljoen jaar oud en het in die Titonium-tydsnede van die Jura voorgekom. *Brontosaurus* is lank beskou as ’n sinoniem vir die *Apatosaurus* en sy tipe-spesie is in 1903 hernoem tot *A. excelsus*.

’n Uitgebreide studie wat in 2015 gepubliseer is, het egter bevind *Brontosaurus* was ’n geldige souropode-genus wat verskil het van *Apatosaurus*. Volgens dieselfde studie is nog twee spesies wat voorheen as *Apatosaurus* beskou is, hernoem tot *Brontosaurus parvus* en *Brontosaurus yahnahpin*.

Beskrywing
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’n Vergelyking tussen ’n mens en drie dinosourusse: *Apatosaurus ajax* (oranje), *A. louisae* (rooi) en *Brontosaurus excelsus* (groen).
Die gemiddelde lengte van ’n *Apatosaurus* was sowat 22,8 meter en die gemiddelde gewig 16,4 ton. Die nekwerwels was korter en swaarder as dié van *Diplodocus*, en die pote se bene was stewiger en langer. Die stert is tydens normale beweging bo die grond gehou.

Nes alle souropodes het *Apatosaurus* net een klou aan elke voorpoot gehad en drie aan elke agterpoot. *Apatosaurus* het "lugsakke" (holtes) in sy bene gehad om die dier ligter te maak. Sy stert is dalk gebruik om soos ’n sweep te klap.

Klassifikasie
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*Apatosaurus* was lid van die familie Diplodocidae, ’n klade van reusagtige souropodes. Die familie sluit van die grootste diere in wat ooit die aarde bewoon het, soos *Diplodocus*, *Supersaurus* en *Barosaurus*. *Apatosaurus* val ook in die subfamilie Apatosaurinae, saam met die *Brontosaurus*.

’n Kladogram van die familie Diplodocidae volgens Tschopp, Mateus en Benson (2015):

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  Diplodocidae  | 

|  |  |
| --- | --- |
|  | *Amphicoelias altus* |
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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  Apatosaurinae  | 

|  |  |
| --- | --- |
|  | Spesie sonder naam |
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|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
|  | 

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| --- | --- |
|  | ***Apatosaurus ajax*** |
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|  | ***Apatosaurus louisae*** |
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| --- | --- |
|  | *Brontosaurus excelsus* |
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| --- | --- |
|  | *Brontosaurus yahnahpin* |
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|  | *Brontosaurus parvus* |
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|  **Diplodocinae**  | 

|  |  |
| --- | --- |
|  | Spesie sonder naam |
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| --- | --- |
|  | *Tornieria africana* |
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| --- | --- | --- | --- | --- | --- | --- | --- |
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| --- | --- |
|  | *Supersaurus lourinhanensis* |
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|  | *Supersaurus vivianae* |
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| --- | --- |
|  | *Leinkupal laticauda* |
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| --- | --- |
|  | *Galeamopus hayi* |
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| --- | --- | --- | --- | --- | --- | --- | --- |
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| --- | --- |
|  | *Diplodocus carnegii* |
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|  | *Diplodocus hallorum* |
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| --- | --- |
|  | *Kaatedocus siberi* |
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|  | *Barosaurus lentus* |
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