Hesperornithiformes

    Hesperornithiforms, the sea parrots and seaguins, most likely evolved during the Cretaceous and are the only group of toothed birds which have survived to the present day. Throughout the intervening time between the clades inception and the present day, the hesperornithiforms have proven quite conservative, and their basic body type has changed little.
    A hesperornithiform resembles nothing so much as a loon stretched and then flattened. These creatures lack the wings of their cousins, the modern birds, and indeed, their foremost appendages have been reduced to jointless paddles. Seaguins' propulsive force is applied by the two hind legs, which are stoutly built, and end in enormous, lobed, feet.

    Sea parrots and seaguins rarely venture onto land, but are forced to make the excursion, periodically, to give birth. These birds are ovoviviparous, but their young are born still encased in the sack-like allentois, and would suffocate in an underwater birth. Thus, seaguin females must climb up onto the land, propelling themselves with sweeps of the feet and a snake-like wriggling of the body, lay their "egg" and then pull the chick free of the confining birth membrane. Further elaboration of this process varies from species to species.

MAREPSITTACINAE (sea parrots)

Sea parrots are close relatives of the piscivorous seaguins, but they have specialized in molluscs for food. A sea parrot uses its robust beaks and large teeth to crack the hard shells of shellfishes and arctic ammonites.

(fig. 1) Common sea parrot, Marepsittacus pelagus (Northern oceans)

Also unlike the seaguins, sea parrots have retained the teeth in their upper jaw. Based on this character, sea parrots are believed to have diverged from the seaguins in the Eocene or early Miocene.

The Walrooster is the largest sea parrot species, weighing about as much as the (much sleeker and longer) imperial seaguin. This is partly because of their rather heavy and robust bones, which help them dive (walroosters are also known to swallow stones for the same purpose).

(fig. 2) Walrooster, Marepsittacus occinerator (Northern Atlantic)

These massive divers live in the arctic sea, feeding mostly on bottom-dwelling molluscs such as shellfishes, which they detach from rocks using their hooked beaks, and crush the shells with their impressive battery of teeth. They also occasionally catch crabs, but hardly ever even try chasing ammonites like their smaller and swifter ancestors. There have also been reported cases of walroosters scavenging. It seems that with their powerful jaws and teeth they can crack the bones to get to the marrow, inaccessible to most predators.

Walroosters can often be seen in large numbers resting on acrtic rocky beaches or ice floats. The males have a very loud and recongizable voice, used during the mating season and related social disputes, which resembles the crowing of a cock.

CALCITRONINAE (seaguins)

Using their feet as paddles, seaguins scull through the water in quick, jerking motions, mimicking the behavior of the squids and fishes that are their principle food. These birds retain teeth only in their lower jaws, and generally possess longer and more pointed beaks than their sea-parrot cousins.

(fig. 3) Hylekki or baltic seaguin, Calcitronis balticus (Baltic sea)

The 5 meter long Emperor seaguin is the largest seaguin species. Though mainly a piscivore, it has been known to hunt the young of the smallest seaquin species.

(fig. 4) Emperor Seaguin, Orcavis imperiosus (Northern Pacific)

Blueflank seaguins are the most common seaguin species in the Arctic. Blueflanks are quite similar to their Cretaceous ansestors, and eat principally cephalopods (including larval baleen-squids ). Nearly half of its length (of 2.5 meters) is head and neck.

(fig. 4) Blueflank seaguin, Orcavis velocinatans (Northern Atlantic).

Daniel Bensen and Matti Aumala

                                                     ,=M. pelagus (Sea parrot )
                      ,=Marepsittinae=Marepsittacus=|
                     |                               `=M. occinerator( Walrooster )
=Hesperornithiformes=|
                     |                    ,=O. velocinatans ( Blueflank seaguin )
                     |                 ,=Orcavis=|
                     |                |    `=O. imperiosis ( Emperor seaguin )
                      `=Calcitroninae=|
                                       `=Calcitrornis balticus ( Hylekki )
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