What traits in conodonts and ostracoderms are derived relative to those in hagfishes and lampreys?

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Conodonts and ostracoderms are extinct groups of early-jawed vertebrates that played significant roles in the evolution of vertebrate features. They share certain derived traits, which are unique to a particular group and have evolved from ancestral traits. Here are the derived traits possessed by conodonts and ostracoderms:

1. Structures Made of Bone or Bone-like Material: Both conodonts and ostracoderms possessed bone or bone-like structures. In conodonts, these structures were called conodont elements, mineralized structures made of calcium phosphate. These elements were part of the conodont apparatus used for feeding. Ostracoderms, on the other hand, had a skeleton composed of bone or bone-like material, which provided support and protection.

2. Brain Divided into Three Regions (in some ostracoderms): Certain ostracoderms had a brain divided into three distinct regions. The three regions were the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon). This division of the brain into regions is an advanced characteristic seen in more complex vertebrates and represents an early step in developing brain complexity.