Legionary Insignia

[Jona Lendering]

The capricorn is also the zodiac signum of LEG XIIII GMV, also raised by Augustus.

And the bull appears to have been the normal sign for Caesarian units. Ritterling has the following list:

Zodiac:
Lion: IIII Flavia, XIII Gemina, XVI?
Scorpio: Praetorian cohortes
Capricorn: I Adiutrix, II Augusta, IIII Macedonica, XIIII Gemina, XXII Primigenia, XXX Ulpia
Pisces: XI Claudia, XXX Ulpia
Aries: I Minervia
Taurus/Bull: I Italica?, III Gallica, IIII Macedonica, VI Victrix, VII Claudia, VIII Augusta, X Fretensis, X Gemina, XXII Primigenia
Gemini: II Italica, VI Ferrata

Non-zodiac:
Eagle: V Macedonica, XIIII Gemina
Hercules: II Taiana
Pegasus: II Adiutrix, II Augustus

Other:
Centaur: II Parthica
Neptune: XI Claudia, XXX Traiana
Boar: I Italica, X Fretensis, XX Victrix
Elephant: V Alaudae?
Stork: III Italica
Trireme: X Fretensis

I hope this helps.