2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/61459We introduce the concept of {\it para-Hopf algebroid} and define their cyclic cohomology in the spirit of Connes-Moscovici cyclic cohomology for Hopf algebras. Para-Hopf algebroids are closely related to, but different from, Hopf algebroids. Their definition is motivated by attempting to define a cyclic cohomology theory for Hopf algebroids in general. We show that many of Hopf algebraic structures, including the Connes-Moscovici algebra $\mathcal{H}_{FM}$, are para-Hopf algebroids.Final version to appear in Letters in Mathematical Physics. The name of the article has been changed. Our new class of bialgebroids are now called ``para-Hopf algebroids''. One new example of bialgebroids, due to Connes and Moscovici, are shown to satisfy our axioms of para-Hopf algebroidsK-Theory and Homologytext