the preervation of embryo and juvenile i a rate occurrence in the foil record. the tiny, delicate keleton are uually cattered by cavenger or detroyed by weathering before they can be foilized. ichthyoaur had a higher chance of being preerved than did terretrial creature becaue, a marine animal, they tended to live in environment le ubject to eroion.
till, their foilization required a uite of factor: a low rate of decay of oft tiue, little cavenging by other animal, a lack of wift current and wave to jumble and carry away mall bone, and fairly rapid burial. given thee factor, ome area have become a treaury of well-preerved ichthyoaur foil.
the depoit at holzmaden, germany, preent an intereting cae for analyi. the ichthyoaur remain are found in black, bituminou marine hale depoited about 190 million year ago. over the year, thouand of pecimen of marine reptile, fih and invertebrate have been recovered from thee rock.
the quality of preervation i outtanding, but what i even more impreive i the number of ichthyoaur foil containing preerved embryo. ichthyoaur with embryo have been reported from 6 different level of the hale in a mall area around holzmaden, uggeting that a pecific ite wa ued by large number of ichthyoaur repeatedly over time.
the embryo are quite advanced in their phyical development; their paddle, for example, are already well formed. one pecimen i even preerved in the birth canal. in addition, the hale contain the remain of many newborn that are between 20 and 30 inche long.WWw.hAOZuowEn.com
why are there o many pregnant female and young at holzmaden when they are o rare elewhere? the quality of preervation i almot unmatched and quarry operation have been carried out carefully with an awarene of the value of the foil. but thee factor do not account for the intereting quetion of how there came to be uch a concentration of pregnant ichthyoaur in a particular place very cloe to their time of giving birth.