ORGANIC MATRIX IN THE PORIFERA AND CNIDARIA: DÉJÀ VU THROUGH A TEMPORAL TELESCOPE
In this report I can add examples from the Porifera and Cnidaria. Although the individual spicules of sponges such as Leucosolenia and Grantia show no signs of internal matrix, the more massive sclerosponges such as Ceratoporella exhibit typical lacy meshworks of matrix. Moreover, some fossil sponges, including Paleozoic Girtyocoelia, Chaetetes, and an unidentified stromatoporoid, have preserved matrix remnants dispersed through recrystallized calcite skeletons. Among cnidarians, the hydrozoans Millepora and Stylaster have matrix, although irregular, while the octocorals Eugorgia and Tubipora, and the scleractinians Oculina and Paracyathus, exhibit a very characteristic lacy mesh. Even a member of the Rugosa, an unidentified horn coral from the Silurian of Gotland, shows remnants of a lacy matrix dispersed through a blocky calcite skeleton.
The physical attributes of the organic matrix observed in these two phyla fit nicely with the general trend of a fundamentally identical material being adapted to more complex functions by the more complex groups of organisms. An unexpected result is the startling capacity for preservation, at least physically, of these organic components.