The Meckelian groove (or Meckel's groove, Meckelian fossa, or Meckelian foramen, or Meckelian canal) is an opening in the medial (inner) surface of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...

(lower jaw) which exposes the Meckelian cartilage.- Palaeos Glossary: M
Modern eutherian mammals (which includes

placental Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...

mammals) do not have a Meckelian groove.

References

Skeletal system {{Musculoskeletal-stub