Herodotus, Histories 3.103

Herodotus ‘is of course mistaken‘.

τὸ μὲν δὴ εἶδος ὁκοῖόν τι ἔχει ἡ κάμηλος, ἐπισταμένοισι τοῖσι Ἕλλησι οὐ συγγράφω· τὸ δὲ μὴ ἐπιστέαται αὐτῆς, τοῦτο φράσω· κάμηλος ἐν τοῖσι ὀπισθίοισι σκέλεσι ἔχει τέσσερας μηροὺς καὶ γούνατα τέσσερα, τά τε αἰδοῖα διὰ τῶν ὀπισθίων σκελέων πρὸς τὴν οὐρὴν τετραμμένα.

I do not describe to the Greeks what kind of form the camel has, since they know it. But I shall tell them this, a thing which they do not know: a camel has in its hind legs four thighbones and four knees; and its genitals are turned towards its tail through its hind legs.