What does testūdō marīna mean in Latin?

testūdō marīna, a noun, means “sea turtle (marine reptile)”.

What is the genitive of testūdō marīna?

The genitive singular is testūdinis marīnae. testūdō marīna is third declension.

In classical Latin, [tɛsˈtuː.doː maˈriː.na]; in ecclesiastical (church) Latin, [tesˈtuː.do maˈriː.na].

nounthird declension

testūdō marīna f (genitive testūdinis marīnae)

Classical[tɛsˈtuː.doː maˈriː.na]Ecclesiastical[tesˈtuː.do maˈriː.na]

sea turtle (marine reptile)
Testudines marinae ne vivere quidem possunt disclusae ab aque natura intereunt aute in humore, nisi aliquadiu (per intervalla) spirent: parere tamen educareq, solent in sicco sic & lutariae testudines, Aristot.Sea turtles cannot even live when cut off from water, but naturally die in the water unless they breathe once in a while (at intervals): yet they give birth and raise children, just as mud-turtles, on dry land (Aristot.).1550s, Conrad Gessner, Historiae Animalium, volume 2, page 114:

From testūdō (“turtle or tortoise”) + marīnus (“marine”).