Bony Skeleton in the Caucasian Salamander, Mertensiella caucasica (Urodela: Salamandridae): Ontogeny and Embryonization Effect

Anna B. Vassilieva, Irina A. Serbinova


Sequence and timing of cranial, axial and limb skeleton bones appearance from late embryonic stages to metamorphosis is studied in the Caucasian salamander Mertensiella caucasica reared under laboratory condition. Some osteological features, such as the complex nature of the nasal and prootic, are firstly described for this species. A number of heterochronies in the skeletal development is observed in partially embryonized M. caucasica as compared with non-embryonized salamandrids (newts). Namely, i) the formation of the first ossifications in the skull, vertebral column and forelimbs is shifted into the embryonic period; ii) vertebral column starts to ossify before the skull; iii) the appearance of provisory skull bones (coronoid and palatine) is slightly delayed. Moreover, the early-larval teeth generation (non-pedicellate teeth) on the jaws shows signs of reduction. Presumably, these features of M. caucasica skeletal ontogeny reflect the very first steps in the evolutionary trend toward the repatterning of the organogenesis related to the embryonization in Urodela.


Salamandridae; Mertertensiella caucasica; skeleton; ontogeny; heterochrony; embryonization

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