and vertebrate that shows evidence of internal fertilization. This has been observed in several new specimens that clearly display sexual dimorphism between males and females in the species. These specimens have been found to either have bone claspers for the males or plates for the females, at the end of their armor plates. Reinterpretation of several more derived placoderms have shown similar structures to the condition in M. dicki. Male claspers anatomy The clasper of M. dicki is a deeply grooved dermal bone that curves laterally at almost a 90 degree angle to the side of the animal. The clasper extends in length laterally from the mid line past the width of the trunk shield. These claspers are fused with the posterior ventrolateral plate and to each other. This would suggest that these claspers were incapable of moving. Additionally' there is a groove located on the ventral surface of the clasper. Current hypotheses suggested that the groove was used for sperm delivery either in the form of a transport channel for the sperm or was used for an encased structure that carried the sperm canal. The male clasper having a width wider than the trunk shield would allow males and females to enter coatis from the side as apposed from other angles. Other placoderms such as ptyctodontid placoderms have similarly shaped claspers. For example, the clasper of Austroptyctodus gardineri is a dermal bone that curves laterally to the side of the animal and resembles a hook. Female genital plate anatomy Female specimens of M. dicki show paired blade-like structures in the same region of the animal that the claspers are in the males. These blades are ornamented with curving ridges and marginal tubercles on their dorsal (internal) surfaces facing the cloacal chamber and are fused to each other and posterior ventral lateral plate as well. The plates are flat and taper to the lateral ends of the transverse ventral ridge inside the lateral lamina of the posterior ventrolateral plate. These blade like structures have been interpreted as female genital plates. These genital plates suggest that they were used as a grip surface for the male clasper to attach to during copulation. Other placoderms such as the antiarch Pterichthyodes milleri, have identical ornamentation on the dorsal surfaces of the genital plate. Additional, the antiarch Bothriolepis sp. display semicircular plates located in the same anatomical area suggesting that these specimens are females