Plato wrote several references to Socrates's appearance. And Diogenes Laertius reports that Plato was called Plato because he was broad shouldered. Are there any ancient sources describing Aristotle's appearance?
See Diogenes Laërtius, Lives and Opinions of Eminent Philosophers: V,1: Aristotle. for description.
But Aristotle lived 384–322 BC and Diogenes ca.180 – 240: five centuries is a lot of time!
In general, portraits and marble statues are not reliable sources; but you can see: Ludovisi's Aristotle a roman copy of an original work of the Greek Lysippos: 4th century BC and personal sculptor to Alexander the Great.
See: J.H. Jongkees, On the Portraits of Aristotle and Menander, Mnemosyne (1965).
To the best of my knowledge there are no "ancient descriptions of Aristotle's appearance". There are a few statues of Aristotle throughout Greece-(especially in Northern Greece, which was Aristotle's home territory before he arrived in Athens to study at The Academy).
Aristotle was born and raised in the Northern Greek town of Stagira. If one visits Stagira, one will see an ancient city in scattered ruins with a statue of Aristotle overlooking it. And, in recent years, Archeologists insist that they discovered the tomb of Aristotle in the town of Stagira.
(While it does not qualify as an "ancient description" of Aristotle, one could visit The Vatican Museum and see Rafael's. "The School of Athens". Of course Rafael lived about 1800 years AFTER Aristotle, so his painted representation of Aristotle was hardly, an archeologically accurate image).