Have you ever wondered how homo sapiens developed different body parts? This new study could help provide detailed insights.
Scientists exploring the subject in vertebrates specifically uncovered palaeontological evidence that supports the pharyngeal basis for the vertebrate shoulder girdle.
A new study aiming to study the origin of vertebrate paired appendages, particularly–shoulder girdles, found a pharyngeal component of the shoulder.
Origins in the pharyngeal region
In vertebrates, the shoulder girdle is the set of bones that connects the upper limbs (such as arms or fins) to the axial skeleton, which includes the spine. The term "pharyngeal component" implies that this particular part of the shoulder girdle has origins in the pharyngeal region.
In simple terms, evidence suggested that a specific portion of the shoulder girdle, possibly a bone or structure, had its developmental origin in the pharyngeal area.
The pharyngeal region is located in the throat area and is associated with structures like gill arches, which are important for breathing and feeding in aquatic vertebrates.
The identification of a pharyngeal component in the shoulder girdle implies a connection between the shoulder structure and the pharyngeal region, providing insights into the evolutionary development of vertebrate anatomy.
Appendages in aquatic vertebrates
The authors exemplified that the paired appendages are widely considered key innovations that enabled new opportunities for controlled swimming and gill ventilation and were prerequisites for the eventual transition from water to land.
“The past 150 years of debate has been shaped by two contentious theories–the ventrolateral fin-fold hypothesis and the archipterygium hypothesis.”
The archipterygium hypothesis suggested that “fins and girdles evolved from an ancestral gill arch.”
The scientists used computed tomography scanning to examine the braincase of Kolymaspis sibirica–an Early Devonian placoderm fish from Siberia.
They identified the origin of the shoulder girdle on the sixth branchial arch by combining the findings with the comparative anatomy of placoderms and jawless outgroups.
This helped the scientists explain the location of the head-trunk interface in jawless fishes. The researchers aimed to contribute to a better understanding of the evolutionary history of vertebrate anatomy and the transition from water to land in vertebrate evolution.
The study was published in the journal Nature on November 1.
The origin of vertebrate paired appendages is one of the most investigated and debated examples of evolutionary novelty1,2,3,4,5,6,7. Paired appendages are widely considered as key innovations that enabled new opportunities for controlled swimming and gill ventilation and were prerequisites for the eventual transition from water to land. The past 150 years of debate8,9,10 has been shaped by two contentious theories4,5: the ventrolateral fin-fold hypothesis9,10 and the archipterygium hypothesis8. The latter proposes that fins and girdles evolved from an ancestral gill arch. Although studies in animal development have revived interest in this idea11,12,13, it is apparently unsupported by fossil evidence. Here we present palaeontological support for a pharyngeal basis for the vertebrate shoulder girdle. We use computed tomography scanning to reveal details of the braincase of Kolymaspis sibirica14, an Early Devonian placoderm fish from Siberia, that suggests a pharyngeal component of the shoulder. We combine these findings with refreshed comparative anatomy of placoderms and jawless outgroups to place the origin of the shoulder girdle on the sixth branchial arch. These findings provide a novel framework for understanding the origin of the pectoral girdle. Our evidence clarifies the location of the presumptive head–trunk interface in jawless fishes and explains the constraint on branchial arch number in gnathostomes15. The results revive a key aspect of the archipterygium hypothesis and help reconcile it with the ventrolateral fin-fold model.
Originally published on Interesting Engineering : Original article