ID Keys

Mytiloidea (500 - 5000m)

#1
Glassy, subquadrate [c1], dorsal margin steep becoming anterior, beaks close to the anterior.
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Thin, modioliform [c2] but beaks set well back from anterior, dorsal and ventral margin subparallel.
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#2
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Posterior dorsal margin finely denticulate [c3] (bathyal).
Dacrydium ockelmanni
  
Posterior and anterior dorsal margins denticulate, denticles as rough parallel bars [c4] (arctic).
Dacrydium vitreum
  
#3
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Thin translucent shells, anterior and posterior dysodont denticles present [c5], with sparse periostracal hairs (woodfall) [c6].
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Thin shell with weak posterior dysodont denticles below ligament [c7], periostracum smooth [c8] (whalefall).
Idas simpsoni
  
#4
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Dorsal and ventral margin subparallel [c9].
Idas argenteus
  
Dorsal and ventral margins at a distinct angle to each other [c10].
Idas lamellosus