Analyses of enantiornithe bone histology have been conducted to determine the growth rates of these animals. A 2006 study of "Concornis" bones showed a growth pattern different from modern birds; although growth was rapid for a few weeks after hatching, probably until fledging, this small species did not reach adult size for a long time, probably several years. Other studies have all supported the view that growth to adult size was slow, as it is in living precocial birds (as opposed to altricial birds, which are known to reach adult size quickly). Studies of the rate of bone growth in a variety of enantiornithines has shown that smaller species tended to grow faster than larger ones, the opposite of the pattern seen in more primitive species like "Jeholornis" and in non-avialan dinosaurs. Some analyses have interpreted the bone histology to indicate that enantiornithines may not have had fully avian endothermy, instead having an intermediate metabolic rate.