Jamna szybiaki

By José Carlos Cortés

Etymology: From Jamna Dolna 

First Described By: Bocheński et al., 2011 

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoriformes, Maniraptora, Pennaraptora, Paraves, Eumaniraptora, Averaptora, Avialae, Euavialae, Avebrevicauda, Pygostylia, Ornithothoraces, Euornithes, Ornithuromorpha, Ornithurae, Neornithes, Neognathae, Neoaves, Australaves, Psittacopasserae, Passeriformes 

Status: Extinct 

Time and Place: Between 31 and 30 million years ago, in the Rupelian of the Oligocene 

Jamna is known from the Pakiet E site of the Menilite Formation in Poland 

Physical Description: Jamna was another early, fairly generalistic passerine, and a small one at that. So, in a lot of ways, it was very similar to yesterday’s Wieslochia. About the size of a dipper or a skylark, it probably didn’t get bigger than 18 centimeters, so a little bit larger than Wieslochia, but not by much. It had short, broad, rounded wings; and a short and rounded tail. With very long and skinny legs, it was able to run fast along the ground, and hop as well. It had a straight, long beak, much like living thrushes. It was a very fluffy bird, like its living relatives, and showcases how perching birds were already doing what they are adapted to do as early as the Oligocene. It had three toes going forward, and one backward – the typical perching form of a passerine. Its sternum was rod-liked and more solid than in its contemporary Wieslochia, and it had broad fingers that gave its wings stronger muscle attachment sites. 

Diet: Jamna was probably an omnivore, eating either insects or fruit, given the shape of its beak. 

Behavior: The short wings and round tail of Jamna allowed it to bob and weave between trees and shrubs, making it a very maneuverable bird and active. Its long legs and general hopping demeanor means it was just as energetic on the ground too, and it would have been a very hyper bird in its environment. Jamna would have also used its energetic nature and well-adapted limbs to escape predators as fast as it could. It probably spent most of its time foraging both on the ground and in the trees, searching for bugs and fruit wherever it could reach – in tree cavities, under leaf litter, and on the undersides of branches. It probably took care of its young, and it is uncertain if it was particularly social. 

Ecosystem: Jamna lived in a fairly dense forest environment, farther away from the coast than that of the contemporary Wieslochia. The Menilite Formation surrounded extensive lake systems, which routinely underwent rapid burial that would suffocate and bury many animals at once. It was filled with a variety of algae and cyanobacteria within the lake itself; and there was a lot of thermal activity going on in the area at the time – including gas bubbles emerging and oil reaching the surface, which negatively affected the local ecosystem. Many different kinds of fish were present here, especially ray-finned fish, which populated the lake system. Other dinosaurs were here too, including the early hummingbird Eurotrochilus, the woodpecker relative Picavus, and another potential passerine, Winnicavis. 

Other: Despite their similarities, Jamna and Wieslochia were quite different, with significant changes in the sternum and other bones that indicate they weren’t particularly closely related. This indicates that there was a wide diversity of perching birds in Europe as early as the Oligocene, and that the fossil record potentially does not well record or reflect that diversity. Whether or not passeriformes reached levels of species richness we see today is another question, and potentially an unanswerable one. 

~ By Meig Dickson

Sources under the Cut