Mytiloida

Malchus, Nikolaus, 2004, Early ontogeny of Jurassic bakevelliids and their bearing on bivalve evolution, Acta Palaeontologica Polonica 49 (1), pp. 85-110 : 90-92

Order Mytiloida

• Mytiloidea: Mytilidae : Mytilinae ( Mytilus ), Musculinae ( Musculus ), Crenellinae ( Crenella ), Dacrydiinae , …

Order Arcoida

• [Cardioloidea: Cardiolidae , Slavidae

• Arcoidea: Parallelodontidae ( Grammatodon ), Noetiidae ( Striarca )

• Limopsoidea: Limopsidae ( Limopsis )]

Order Cyrtodontoida

• Cyrtodontoidea: Cyrtodontidae (cyrtodontids unspecified, …

Order Pectinoida

• [Monotoidea: Oxytomidae ( Oxytoma , Meleagrinella ), …]

[Order Praecardioida *

• Praecardioidea: Praecardiidae , Antipleuridae *, Praeostreidae *, Butovicellidae *, Lunulacardiidae * (after Yancey and Heaney 2000)

• Inoceramoidea: Inoceramidae *, … (after Johnston and Collom 1998)]

Superfamily Ambonychioidea *

• [ Inoceramidae *, …]

Order Pterioida *

• Pterioidea

• Pterineidae

• [ Bakevelliidae *, Cassianellidae *, Lithiotidae , Pteriidae *, Dattidae , Isognomonidae *, Retroceramidae , Pulvinitidae (*), Malleidae *,...]

• [Pinnoidea (? Atrina (*))]

Order Ostreoida *

• [? Lopha –Enantiostreon −stock

• Ostreoidea*

• Gryphaeoidea*

•? Chondrodontidae stock]

Fig. 3. A–C. Morphotype 4. A. RV, earliest nepioconch stage, BGR X10856−9; A 1, incipient nacreous shell layers, arrow points at rather straight poste− Ą rior−ventral shell margin, × 60; A 2, close up of hinge, arrow points at post−larval fibrous ligament, which is detached from the still preserved row of larval denticles, × 200. B. P2−LV, BGR X10849−6; B 1, dorsal, close up view of umbo, arrow indicates approximate position of pd−outlet, which is not accompanied by a notch as in oysters (compare Fig. 6C 2), × 250; B 2, internal view, arrow indicates position of pd−outlet, × 100. C. P2−LV, BGR X10855−5, × 100.

D–H. Morphotype 5. D. P2−LV, BGR X10855−4, × 100. E. P2−RV, BGR X10855−3, × 100. F. BGR X10838−5; F 1, P2−LV, arrow indicates pd−outlet, × 100;

F 2: close up of pd−outlet, × 700. G. Close up of pd−outlet (white arrows) and incipient secondary denticles (black arrow) of a P2−RV, BGR X10856−5, × 700.

H. P2−RV, BGR X10856−4; H 1, entire valve, long arrow indicates position of pd−outlet, short arrow region of marked secondary denticles; H 2, close up of shell margin with secondary denticles, × 700. I. Morphotype 6, P2−LV, BGR X10846−1, × 100.

One of the few taxa that have not yet been linked to the Bakevelliidae are the Inoceramidae . According to Carter (1990: 199), this family belongs to the Ambonychioidea rather than Pterioida . Johnston and Collom (1998) placed the Inoceramidae in their amended order Praecardioida which, together with the Solemyoida constitute their subclass Cryptodonta (compare with Table 1). However, most recent phylogenetic analyses suggest that the Solemyoidea are the sister taxon of the Nuculoidea ( Waller 1998: node PR2 and fig. 3; Giribet and Wheeler 2002: fig. 7) or that they evolved from nuculoid ancestors ( Carter et al. 2000; Carter 2001), and hence should be included in the subclass Palaeotaxodonta. In addition, the Praecardioida sensu Johnston and Collom (1998) probably incorrectly contain the Cardiolidae , which is based on doubtful homologies of hinge characters between this family and the Inoceramidae (personal observations). The Cardiolidae are more likely related to the Arcoida (see Carter 1990: 181). However, this does not preclude the possibility that the Inoceramidae belong to the Praecardioida (see phylogenetic implications, below).