The biserial archipterygium consists of a segmented axial rod, bearing a praeaxial and a postaxial series of jointed rays.
The skeleton of the free limb is probably seen in its most archaic form amongst existing fishes in the biserial archipterygium of Ceratodus (fig.
Hydrothecae sessile, biserial on the main stem, uniserial on the lateral branches or pinnules, which give the colony its characteristic feathery form; with nematophores.
On the other hand, a polyp on the main stem may form a second bud which, instead of forming a pinnule by uniserial budding, produces by biserial budding a branch, from which pinnules arise as from the main stem (fig.
In this way are formed the familiar feathery colonies of Plumularia, in which the pinnules are all in one plane, while in the allied Antennularia the pinnules are arranged in whorls round the main biserial stem.
Hence the colonies of Calyptoblastea may be complexly branched, and the budding may be biserial throughout, uniserial throughout, or partly one, partly the other.
Skeleton of the breast-fin of Ceratodus (biserial feathered skeleton).
We find the same biserial primitive fin more or less preserved in the fossilised remains of the earliest Selachii (Figure 2.
Both the breast-fin and the belly-fin are flat oval paddles, in which we find a biserialcartilaginous skeleton (Figure 2.
They are possessed of dermal bones and other ossifications, and are characterized by their lobate paired fins, which have a thick axis beset with biserial fin rays.
This biserial archipterygium with its limb-girdle is derived from a series of gill-rays attached to a branchial arch.
The Cladodontidae differ in having the "pectoral fin developed in the form of a uniserial archipterygium intermediate between the truly biserial one of Pleuracanthus and the pectoral fin of modern sharks.
In their disposition they are either uniserial, biserial or multiserial.
When they are arranged in uniserial or biserial rows the genital ducts open into or near the branchial grooves in the region of the pharynx and in a corresponding position in the post-branchial region.
This biserial investment of rays on the stem of the fin may also undergo various kinds of modifications.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "biserial" in a variety of sentences. We hope that you will now be able to make sentences using this word.
